Functional organization of human intraparietal and frontal cortex for attending, looking, and pointing

A fronto-parietal network is mediating improvement of motor function related to repetitive peripheral magnetic stimulation: A PET-H2O15 study

Repetitive peripheral magnetic stimulation (RPMS) is a focused and painless stimulation method, in which muscle contractions are elicited by depolarization of the terminal motor branches. Clinical-experimental investigations on different disorders of sensorimotor integration in the last decade have shown that RPMS can be used for the rehabilitation of motor functions after stroke. It is supposed that this therapeutic effect is based on the RPMS-induced proprioceptive inflow to the CNS. To analyze the conditioning effects of RPMS on reorganization of the motor system on cortical level positron emission tomography (PET) is used. Regional cerebral blood flow (rCBF) has been measured using H(2)O(15)-PET in eight patients with arm paresis following focal cerebral ischemic infarction before and after treatment using RPMS on upper arm flexor muscles. Behavioral measures showed a significant improvement of kinematics of finger movements and a reduction of spasticity in the affected arm following RPMS treatment. The recovery was associated with significant increase of neural activation within the superior posterior parietal lobe and the premotor cortex (PM) areas. The increase of activation of the parieto-premotor network following RPMS treatment indicates a significant conditioning effect of RPMS on the cortical level. These results emphasize the positive therapeutic effect of RPMS and describe the physiological bases of its function on the central level.

EEG dynamics of the frontoparietal network during reaching preparation in humans

Visuomotor transformation processes are essential when accurate reaching movements towards a visual target have to be performed. In contrast, those transformations are not needed for similar, but non-visually guided, arm movements. According to previous studies, these transformations are carried out by neuronal populations located in the parietal and frontal cortical areas (the so-called "dorsal visual stream"). However, it is still debated whether these processes are mediated by the sequential and/or parallel activation of the frontoparietal areas. To investigate this issue, we designed a task where the same visual cue could represent either the target of a reaching/pointing movement or the go-signal for a similar but non-targeting arm movement. By subtracting the event-related potentials (ERPs) recorded from healthy subjects performing the two conditions, we identified the brain processes underlying the visuomotor transformations needed for accurate reaching/pointing movements. We then localized the generators by means of cortical current density (CCD) reconstruction and studied their dynamics from visual cue presentation to movement onset. The results showed simultaneous activation of the parietal and frontal areas from 140 to 260 ms. The results are interpreted as neural correlates of two critical phases of visuomotor integration, namely target selection and movement selection. Our findings suggest that the visuomotor transformation processes required for correct reaching/pointing movements do not rely on a purely sequential activation of the frontoparietal areas, but mainly on a parallel information processing system, where feedback circuits play an important role before movement onset.

Amblyopie fonctionnelle : évaluation en IRM fonctionnelle de la réponse corticale visuelle après traitement

PURPOSE

Functional MRI evaluation of the cortical response in treated amblyopic patients.

MATERIAL AND METHODS

Clinical and functional MRI exploration of ten patients, seven men and three women aged from 21 to 59 years, with strabismus management during childhood. Functional evaluations were performed on a 1.5 Tesla MR device, with four monocular functional sessions, two stimulations per eye. Alternating rest and active phases displayed still and flickering black and white checkerboards with spatial and temporal frequencies of 1 degree/8Hz and 15'/4Hz. Anatomical realignment and statistical analysis were performed using SPM99 (Statistical Parametric Mapping) to compare the four sessions in individuals.

RESULTS AND DISCUSSION

In patients presenting a visual acuity of the amblyopic eye less than 0.7, stimulation of this eye induced lower response in V1, V3, and V5 in comparison with the contralateral eye stimulation. Unexpectedly, in patients recovering normal or subnormal acuity, the amblyopic eye gave comparable or enhanced response in these areas. Additional response was found in the secondary visual cortex, the cuneus, the lingual gyrus, and in parietal, frontal, and orbitofrontal areas. These results suggest a variation in cortical response depending on the efficacy of the treatment. Recovered amblyopic eye, even with acuity less than the contralateral eye, may induce a reinforced cortical sensitivity to visual stimulus. Secondary visual areas may contribute to an attentional process in image perception and analysis. Cortical plasticity may be observed several years after amblyopia treatment.

CONCLUSION

Our study substantiates the importance of an effective and early treatment of functional amblyopia, inducing cortical plasticity with reinforced attention and sensitivity to visual perception.

Motor brain regions are involved in the encoding of delayed intentions: a fMRI study

In studies of prospective memory, recall of the content of delayed intentions is normally excellent, probably because they contain actions that have to be enacted at a later time. Action words encoded for later enactment are more accessible from memory than those encoded for later verbal report [Freeman, J.E., and Ellis, J.A. 2003a. The representation of delayed intentions: A prospective subject-performed task? Journal of Experimental Psychology: Learning, Memory, and Cognition, 29, 976-992.]. As this higher assessibility is lost when the intended actions have to be enacted during encoding, or when a motor interference task is introduced concurrent to intention encoding, Freeman and Ellis suggested that the advantage of to-be-enacted actions is due to additional preparatory motor operations during encoding. Accordingly, in a fMRI study with 10 healthy young participants, we investigated whether motor brain regions are differentially activated during verbal encoding of actions for later enactment with the right hand in contrast to verbal encoding of actions for later verbal report. We included an additional condition of verbal encoding of abstract verbs for later verbal report to investigate whether the semantic motor information inherent in action verbs in contrast to abstract verbs activates motor brain regions different from those involved in the verbal encoding of actions for later enactment. Differential activation for the verbal encoding of to-be-enacted actions in contrast to to-be-reported actions was found in brain regions known to be involved in covert motor preparation for hand movements, i.e. the postcentral gyrus, the precuneus, the dorsal and ventral premotor cortex, the posterior middle temporal gyrus and the inferior parietal lobule. There was no overlap between these brain regions and those differentially activated during the verbal encoding of actions in contrast to abstract verbs for later verbal report. Consequently, the results of this fMRI study suggest the presence of preparatory motor operations during the encoding of delayed intentions requiring a future motor response, which cannot be attributed to semantic information inherent to action verbs.

When Gaze Turns into Grasp

Previous research has provided evidence for a neural system underlying the observation of another person's hand actions. Is the neural system involved in this capacity also important in inferring another person's motor intentions toward an object from their eye gaze? In real-life situations, humans use eye movements to catch and direct the attention of others, often without any accompanying hand movements or speech. In an event-related functional magnetic resonance imaging study, subjects observed videos showing a human model either grasping a target object (grasping condition) or simply gazing (gaze condition) at the same object. These two conditions were contrasted with each other and against a control condition in which the human model was standing behind the object without performing any gazing or grasping action. The results revealed activations within the dorsal premotor cortex, the inferior frontal gyrus, the inferior parietal lobule, and the superior temporal sulcus in both “grasping” and “gaze” conditions. These findings suggest that signaling the presence of an object through gaze elicits in an observer a similar neural response to that elicited by the observation of a reach-to-grasp action performed on the same object.

Individuals with schizophrenia present hypo- and hyperactivation during implicit cueing in an inhibitory task

BACKGROUND

The primary purpose of this investigation was to assess the neural correlates of implicit cueing during an inhibitory task in schizophrenia when performance accuracy was matched with healthy comparison subjects.

METHODS

We compared 17 individuals with chronic schizophrenia (SZ; medicated, 13.9 average years of illness) and 17 healthy comparison subjects (HC) matched for hit and false alarm rates, age, and education on a visual Go/Nogo task during functional magnetic resonance imaging. In this task, one of the go stimuli also served implicitly as a cue predictive of a subsequent inhibitory (Nogo) trial.

CONCLUSIONS

Findings suggest that even when matched for overall performance accuracy, individuals with SZ exhibit difficulties with inhibition and cue processing that may relate to core deficits in cognitive control and stimulus processing. In particular, these findings point towards an important role of the parietal cortex for cued inhibitory processes in healthy populations.

A human parietal face area contains aligned head-centered visual and tactile maps

Visually guided eating, biting and kissing, and avoiding objects moving toward the face and toward which the face moves require prompt, coordinated processing of spatial visual and somatosensory information in order to protect the face and the brain. Single-cell recordings in parietal cortex have identified multisensory neurons with spatially restricted, aligned visual and somatosensory receptive fields, but so far, there has been no evidence for a topographic map in this area. Here we mapped the organization of a multisensory parietal face area in humans by acquiring functional magnetic resonance images while varying the polar angle of facial air puffs and close-up visual stimuli. We found aligned maps of tactile and near-face visual stimuli at the highest level of human association cortex-namely, in the superior part of the postcentral sulcus. We show that this area may code the location of visual stimuli with respect to the face, not with respect to the retina.

Integration of target and effector information in the human brain during reach planning

To plan a reaching movement, the brain must integrate information about the location of the target with information about the limb selected for the reach. Here, we applied rapid event-related 3-T fMRI to investigate this process in human subjects (n = 16) preparing a reach following two successive visual instruction cues. One cue instructed which arm to use; the other cue instructed the location of the reach target. We hypothesized that regions involved in the integration of target and effector information should not only respond to each of the two instruction cues, but should respond more strongly to the second cue due to the added integrative processing to establish the reach plan. We found bilateral regions in the posterior parietal cortex, the premotor cortex, the medial frontal cortex, and the insular cortex to be involved in target-arm integration, as well as the left dorsolateral prefrontal cortex and an area in the right lateral occipital sulcus to respond in this manner. We further determined the functional properties of these regions in terms of spatial and effector specificity. This showed that the posterior parietal cortex and the dorsal premotor cortex specify both the spatial location of a target and the effector selected for the response. We therefore conclude that these regions are selectively engaged in the neural computations for reach planning, consistent with the results from physiological studies in nonhuman primates.

Spontaneous neuronal activity distinguishes human dorsal and ventral attention systems

On the basis of task-related imaging studies in normal human subjects, it has been suggested that two attention systems exist in the human brain: a bilateral dorsal attention system involved in top-down orienting of attention and a right-lateralized ventral attention system involved in reorienting attention in response to salient sensory stimuli. An important question is whether this functional organization emerges only in response to external attentional demands or is represented more fundamentally in the internal dynamics of brain activity. To address this question, we examine correlations in spontaneous fluctuations of the functional MRI blood oxygen level-dependent signal in the absence of task, stimuli, or explicit attentional demands. We identify a bilateral dorsal attention system and a right-lateralized ventral attention system solely on the basis of spontaneous activity. Further, we observe regions in the prefrontal cortex correlated with both systems, a potential mechanism for mediating the functional interaction between systems. These findings demonstrate that the neuroanatomical substrates of human attention persist in the absence of external events, reflected in the correlation structure of spontaneous activity.

Visuo-motor integration and control in the human posterior parietal cortex: evidence from TMS and fMRI

The posterior parietal cortex is a fundamental structure for visuo-motor integration and control. Here I discuss recent transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) studies that I interpret as suggesting four concepts. The evolutionary process has enlarged the human posterior parietal cortex while still preserving the internal structure of the posterior parietal cortex of other primates. Visuo-motor control in the posterior parietal cortex may be implemented by coding primarily action goals. The lateralization of visuo-motor functions in the posterior parietal cortex suggests that the left posterior parietal cortex is more concerned with tool use and the right posterior parietal cortex is more concerned with imitation of the actions of others. Finally, visuo-motor inter-hemispheric transfer through parietal callosal fibers occurs at the level of 'motor intention'.

Feature-based attention in visual cortex

Although most studies of visual attention have examined the effects of shifting attention between different locations in the visual field, attention can also be directed to particular visual features, such as a color, orientation or a direction of motion. Single-unit studies have shown that attention to a feature modulates neuronal signals in a range of areas in monkey visual cortex. The location-independent property of feature-based attention makes it particularly well suited to modify selectively the neural representations of stimuli or parts within complex visual scenes that match the currently attended feature. This review is part of the TINS special issue on The Neural Substrates of Cognition.

The neural mechanisms underlying the Müller-Lyer illusion and its interaction with visuospatial judgments

Arrows terminating a line can distort the perceived line length. This so-called Müller-Lyer illusion can be used in healthy human subjects to mimic the performance of neglect patients in visuospatial judgments (e.g., in the landmark task). In this study, we investigated the neural mechanisms underlying the Müller-Lyer illusion, the landmark task, and their interaction. This was achieved by parametrically manipulating the magnitude of the Müller-Lyer illusion both in a landmark and in a luminance (control) task. As expected, the landmark task activated right posterior parietal cortex and right temporo-occipital cortex. In contrast, the neural processes associated with the strength of the Müller-Lyer illusion were located bilaterally in the lateral occipital cortex as well as the right superior parietal cortex. The data not only converge with but also extend neuropsychological data that indicate maintained line-length illusion in neglect patients. In addition, our results support the size-constancy scaling hypothesis as a putative mechanism underlying line-length illusions. Furthermore, activation that was driven by both the task and the strength of the Müller-Lyer illusion was observed in right intraparietal sulcus, thus arguing in favor of an interaction of illusory information with the top-down processes underlying visuospatial judgments in right parietal cortex.

Audio-visual multisensory integration in superior parietal lobule revealed by human intracranial recordings

Intracranial recordings from three human subjects provide the first direct electrophysiological evidence for audio-visual multisensory processing in the human superior parietal lobule (SPL). Auditory and visual sensory inputs project to the same highly localized region of the parietal cortex with auditory inputs arriving considerably earlier (30 ms) than visual inputs (75 ms). Multisensory integration processes in this region were assessed by comparing the response to simultaneous audio-visual stimulation with the algebraic sum of responses to the constituent auditory and visual unisensory stimulus conditions. Significant integration effects were seen with almost identical morphology across the three subjects, beginning between 120 and 160 ms. These results are discussed in the context of the role of SPL in supramodal spatial attention and sensory-motor transformations.

Recovering Space in Unilateral Neglect: A Neurological Dissociation Revealed by Virtual Reality

Neglect patients often show deficits in responding to targets in the contralesional side of space. Past studies were able to ameliorate these deficits through manipulation of visual input. Here, the neural bases of the recovery of space following virtual reality (VR) training in neglect patients were investigated. Neglect patients were trained to respond to targets in the left side of space that appeared in the central or in the right side of space in a VR system. It was found that only patients with lesions that spared the inferior parietal/superior temporal regions were able to benefit from the VR training. It was concluded that these regions play a crucial role in the recovery of space that underlies the improvement of neglect patients when trained with VR. The implications of these results for determining the neural bases of a higher order attentional and/or spatial representation and for treating patients with unilateral neglect are discussed.

Visuospatial reorienting signals in the human temporo-parietal junction are independent of response selection

This study contrasts visuospatial reorienting and response selection signals in the right temporo-parietal junction (TPJ) with functional magnetic resonance imaging. The overall goal was to investigate whether spatial orienting signals and motor signals interacted or were independent in TPJ. The right TPJ showed a greater response to targets at in-validly rather than validly cued locations, but no significant modulation from the effector used to respond. We suggest that TPJ may work as a modality-independent 'circuit breaker' for the dorsal fronto-parietal attention system, directing attention to salient events and enabling a variety of responses to those events.

Sustained attention and apical dendrite activity in recurrent circuits

Recurrent neural activity is a pervasive mode of cortical operations and is believed to underlie cognitive functions of working memory, attention, and the generation of spontaneous activity during sleep . It is proposed here that activity in corticothalamic recurrent circuits underlies the sustaining of attention, and that extended durations of attention are made possible by the stabilizing effects of electrical activity in long apical dendrites of pyramidal neurons. Using the cue-target delay task as a framework, the present paper describes sustained attention during the cue-target delay as activity in recurrent circuits involving layer 5/6 pyramidal neurons. At target onset, persistent activity in apical dendrites of layer 2/3 pyramidal neurons (projected from the recurrent circuits) can enhance the processing of incoming pulse trains at basal dendrites. Apical dendrite activity is assumed to modulate the soma processing of layer 2/3 and layer 5/6 pyramidal neurons at subthreshold voltage levels. The variability of successive soma depolarizations from the apical dendrite strongly influences the stability of activity in the corticothalamic recurrent circuit. Lower variability promotes higher stability. According to the present model of apical dendrite function, soma depolarizations can be reduced in variability and maintained within subthreshold levels by increasing the distance that EPSPs propagate along the apical dendrite. The close relationship between sustained attention and the electrical field potentials produced by repeated EPSP propagations in apical dendrites is supported in a brief review of sustained attention experiments that have employed measures of EEG, ERS/ERD, ERP, and LFP.

Human parietal cortex in action

Experiments using functional neuroimaging and transcranial magnetic stimulation in humans have revealed regions of the parietal lobes that are specialized for particular visuomotor actions, such as reaching, grasping and eye movements. In addition, the human parietal cortex is recruited by processing and perception of action-related information, even when no overt action occurs. Such information can include object shape and orientation, knowledge about how tools are employed and the understanding of actions made by other individuals. We review the known subregions of the human posterior parietal cortex and the principles behind their organization.

Precuneus is involved in allocentric spatial location encoding and recognition

Using a declarative memory paradigm, the anatomical correlates of spatial location encoding and retrieval in the healthy human brain as reflected by BOLD fMRI were investigated. During encoding, subjects were instructed to view and keep in mind different locations of an object on a platform seen from different viewpoints in virtual 3D. In retrieval trials, subjects had to recognize previously learned object locations. Comparing activation patterns associated with encoding and recognition on a voxel-by-voxel basis, we found regions in the precuneus bilaterally activated by both processes. To our knowledge, this is the first study that directly compared human brain activation patterns associated with allocentric encoding and retrieval of spatial locations in virtual 3D. Our results provide further information concerning the role of the precuneus in declarative memory processes, pointing to precuneus involvement in encoding and retrieval of spatial locations.

Functional clusters in the human parietal cortex as revealed by an observer-independent meta-analysis of functional activation studies

The human parietal cortex is a highly differentiated structure consisting of cytoarchitectonically defined subareas that are specifically connected with other cortical and subcortical areas. Based on evidence from neurophysiological studies in subhuman primates these subareas are supposed to be functionally highly specialized. Here, we reviewed 51 different neuroimaging studies on healthy subjects with activation of the parietal lobe in statistical parametric maps. Running a cluster analysis on the stereotactic coordinates of the centers of gravity of the activation areas and plotting them into Talairach space showed a high consistency of the mean activation foci for similar paradigms across different laboratories and functional imaging modalities. Our meta-analysis exposed seven distinct pairs of quite symmetrically distributed subareas of the parietal cortex of each hemisphere as well as three unpaired regions that are critically involved in the generation of limb and eye movements in egocentric and allocentric coordinates, but also in attention, memory and cognitive problem solving. These data highlights the modular organization of the human parietal lobe. By its locally interspersed distributed circuits it orchestrates specialized cognitive subfunctions interfacing perception and action. Our meta-analysis provides a new framework for understanding information processing in the human parietal cortex.

TMS in the parietal cortex: updating representations for attention and action

Transcranial magnetic stimulation (TMS) is one of the most recent techniques to have been used in investigations of the parietal cortex but already a number of studies have employed it as a tool in investigations of attentional and sensorimotor processes in the human parietal cortices. The high temporal resolution of TMS has proved to be a particular strength of the technique and the experiments have led to hypotheses about when circumscribed regions of parietal cortex are critical for specific attentional and sensorimotor processes. A consistent theme that runs through many reports is that of a critical contribution of parietal areas when attention or movements are re-directed and representations for attention or action must be updated.

Spatiotemporal overlap between brain activation related to saccade preparation and attentional orienting

Recent brain imaging studies provided evidence that the brain areas involved with attentional orienting and the preparation of saccades largely overlap, which may indicate that focusing attention at a specific location can be considered as an unexecuted saccade towards that location (i.e. the premotor theory of attention). Alternatively, it may be proposed that attentional orienting is simply relevant for preparing saccades, but the two processes may also be completely unrelated. In two experiments, we examined temporal activation of brain areas by measuring the electroencephalogram. Central cues indicated the likely side (left or right) at which a to-be-attended target would occur, or to which a saccade had to be prepared. Cue direction-related activity was determined, time-locked to cue onset. In addition, in our second experiment, delayed saccades had to be carried out, which allows to focus on processes strongly related to saccade execution. In nearly all tasks, an early directing attention negativity (EDAN), an anterior directing attention negativity (ADAN), and a late directing attention positivity (LDAP) were observed, time-locked to cue onset. Source analyses supported the view that this activity probably originates from areas within the ventral intraparietal sulcus (vIPS) and the frontal eye fields (FEF). The saccade-locked analysis also indicated that the FEF plays an important role in triggering saccades, but the role of vIPS appears to be minimal. The latter finding disfavors the premotor theory of attention, as it suggests that the relation between attention and action is less direct.

The precuneus: a review of its functional anatomy and behavioural correlates

Functional neuroimaging studies have started unravelling unexpected functional attributes for the posteromedial portion of the parietal lobe, the precuneus. This cortical area has traditionally received little attention, mainly because of its hidden location and the virtual absence of focal lesion studies. However, recent functional imaging findings in healthy subjects suggest a central role for the precuneus in a wide spectrum of highly integrated tasks, including visuo-spatial imagery, episodic memory retrieval and self-processing operations, namely first-person perspective taking and an experience of agency. Furthermore, precuneus and surrounding posteromedial areas are amongst the brain structures displaying the highest resting metabolic rates (hot spots) and are characterized by transient decreases in the tonic activity during engagement in non-self-referential goal-directed actions (default mode of brain function). Therefore, it has recently been proposed that precuneus is involved in the interwoven network of the neural correlates of self-consciousness, engaged in self-related mental representations during rest. This hypothesis is consistent with the selective hypometabolism in the posteromedial cortex reported in a wide range of altered conscious states, such as sleep, drug-induced anaesthesia and vegetative states. This review summarizes the current knowledge about the macroscopic and microscopic anatomy of precuneus, together with its wide-spread connectivity with both cortical and subcortical structures, as shown by connectional and neurophysiological findings in non-human primates, and links these notions with the multifaceted spectrum of its behavioural correlates. By means of a critical analysis of precuneus activation patterns in response to different mental tasks, this paper provides a useful conceptual framework for matching the functional imaging findings with the specific role(s) played by this structure in the higher-order cognitive functions in which it has been implicated. Specifically, activation patterns appear to converge with anatomical and connectivity data in providing preliminary evidence for a functional subdivision within the precuneus into an anterior region, involved in self-centred mental imagery strategies, and a posterior region, subserving successful episodic memory retrieval.

Cortico-cortical networks and cortico-subcortical loops for the higher control of eye movements

There are multiple distinct regions, or eye fields, in the cerebral cortex that contribute directly to the initiation and control of voluntary eye movements. We concentrate on six of these: the frontal eye field, parietal eye field, supplementary eye field, middle superior temporal area, prefrontal eye field, and area 7 m (precuneus in humans). In each of these regions: (1) there is neural activity closely related to eye movements; (2) electrical microstimulation produces or modifies eye movements; (3) surgical lesions or chemical inactivation impairs eye movements; (4) there are direct neural projections to major structures in the brainstem oculomotor system; and (5) increased activity is observed during eye movement tasks in functional magnetic resonance imaging or positron emission tomography experiments in humans. Each of these eye fields is reciprocally connected with the other eye fields, and each receives visual information directly from visual association cortex. Each eye field has distinct subregions that are concerned with either saccadic or pursuit eye movements. The saccadic subregions are preferentially interconnected with other saccade subregions and the pursuit subregions are preferentially interconnected with other pursuit subregions. Current evidence strongly supports the proposal that there are parallel cortico-cortical networks that control purposeful saccadic and pursuit eye movements, and that the activity in those networks is modulated by feedback information, via the thalamus, from the superior colliculus, basal ganglia, and cerebellum.

MRI and fMRI analysis of oculomotor function

This chapter reviews the anatomical correlations of the cortical oculomotor centers in humans. The modern structural methods allow a better anatomical definition of the parietal, frontal and temporal structures involved in oculomotor control. Functional imaging reveals the cortical networks involved in saccadic, pursuit, and vestibular eye movements. Finally, the interaction of the network between attention and eye movements is discussed.

The left parietal cortex and motor intention: An event-related functional magnetic resonance imaging study

Traditionally the posterior parietal cortex was believed to be a sensory structure. More recently, however, its important role in sensory-motor integration has been recognized. One of its functions suggested in this context is the forming of intentions, i.e. high-level cognitive plans for movements. The selection and planning of a specific movement defines motor intention. In this study we used rapid event-related functional magnetic resonance imaging of healthy human subjects to investigate the involvement of posterior parietal cortex in motor intention in response to valid imperative cues. Subjects were provided with either neutral, motor or spatial cues. Neutral cues simply alerted, motor cues indicated which hand to use for response, and spatial cues indicated on which side the target would appear. Importantly, identical targets and responses followed these cues. Therefore any differential neural effects observed are independent from the actual movement performed. Differential blood oxygen level dependent signal changes for motor vs. neutral as well as motor vs. spatial cue trials were found in the left supramarginal gyrus, as hypothesized. The results demonstrate that neural activity in the left supramarginal gyrus underlies motor plans independent from the execution of the movement and thus extend previous neuropsychological and functional imaging data on the role of the left supramarginal gyrus in higher motor cognition.

Differences of monkey and human overt attention under natural conditions

Rhesus monkeys are widely used as animal models of human attention. Such research rests upon the assumption that similar mechanisms underlie attention in both species. Here, we directly compare the influence of low-level stimulus features on overt attention in monkeys and humans under natural conditions. We recorded eye-movements in humans and rhesus monkeys during free-viewing of natural images. We find that intrinsic low-level features, such luminance-contrast, texture-contrast and saliency-as predicted by a standard model, are elevated at fixation points in the majority of images. These correlative effects are not significantly different between species. However, local image modifications affect both species differently: moderate modifications, which are in the range of natural fluctuations, attract overt attention in monkeys significantly stronger than they do in humans. In addition, humans show a higher inter-individual consistency regarding which locations they fixate than monkeys, in spite of the similarity for intrinsic low-level features. Taken together, these data demonstrate that-under natural conditions-low-level stimulus features affect attention in monkeys and humans differently.

Mapping the parietal cortex of human and non-human primates

The present essay reviews a series of functional magnetic resonance imaging (fMRI) studies conducted in parallel in humans and awake monkeys, concentrating on the intraparietal sulcus (IPS). MR responses to a range of visual stimuli indicate that the human IPS contains more functional regions along its anterior-posterior extent than are known in the monkey. Human IPS includes four motion sensitive regions, ventral IPS (VIPS), parieto-occipital IPS (POIPS), dorsal IPS medial (DIPSM) and dorsal IPS anterior (DIPSA), which are also sensitive to three-dimensional structure from motion (3D SFM). On the other hand, the monkey IPS contains only one motion sensitive area (VIP), which is not particularly sensitive to 3D SFM. The human IPS includes four regions sensitive to two-dimensional shape and three representations of central vision, while monkey IPS appears to contain only two shape sensitive regions and one central representation. These data support the hypothesis that monkey LIP corresponds to the region of human IPS between DIPSM and POIPS and that a portion of the anterior part of human IPS is evolutionarily new. This additional cortical tissue may provide the capacity for an enhanced visual analysis of moving images necessary for sophisticated control of manipulation and tool handling.

The role of parietal cortex in visuomotor control: what have we learned from neuroimaging?

Research from macaque neurophysiology and human neuropsychology has implicated the parietal cortex in the sensory control of action. Functional neuroimaging has been very valuable in localizing and characterizing specific regions of the human brain involved in visuomotor actions involving different effectors, such as the eyes, head, arms and hands. Here, we review the areas discovered by human neuroimaging, including the putative functional equivalents of the following macaque regions: parietal eye fields (PEF), ventral intraparietal (VIP) area, parietal reach region (PRR) and the anterior intraparietal (AIP) area. We discuss the challenges of studying realistic movements in the imaging environment, the lateralization of visuomotor function, caveats involved in proposing interspecies homologies and the limitations and future directions for neuroimaging studies of visuomotor control.

Two Cortical Systems for Reaching in Central and Peripheral Vision

Parietal lesions in humans can produce a specific disruption of visually guided hand movement, termed optic ataxia. The fact that the deficit mainly occurs in peripheral vision suggests that reaching in foveal and extrafoveal vision rely on two different neural substrates. In the present study, we have directly tested this hypothesis by event-related fMRI in healthy subjects. Brain activity was measured when participants reached toward central or peripheral visual targets. Our results confirm the existence of two systems, differently modulated by the two conditions. Reaching in central vision involved a restricted network including the medial intraparietal sulcus (mIPS) and the caudal part of the dorsal premotor cortex (PMd). Reaching in peripheral vision activated in addition the parieto-occipital junction (POJ) and a more rostral part of PMd. These results show that reaching to the peripheral visual field engages a more extensive cortical network than reaching to the central visual field.

Spatial interference during bimanual coordination: differential brain networks associated with control of movement amplitude and direction

Bimanual interference emerges when spatial features, such as movement direction or amplitude, differ between limbs, as indicated by a mutual bias of limb trajectories. Although first insights into the neural basis of directional interference have been revealed recently, little is known about the neural network associated with amplitude interference. We investigated whether amplitude versus directional interference activates differential networks. Functional magnetic resonance imaging (fMRI) was applied while subjects performed cyclical, bimanual joystick movements with either the same vs. different amplitudes, directions, or both. The kinematic analysis confirmed that subjects experienced amplitude interference when they moved with different as compared to the same amplitude, and directional interference when they moved along different as compared to the same direction. On the brain level, amplitude and directional interference both resulted in activation of a bilateral superior parietal-premotor network, which is known to contribute to sensorimotor transformations during goal-directed movements. Interestingly, amplitude but not directional interference exclusively activated a bilateral network containing the dorsolateral prefrontal cortex, anterior cingulate, and supramarginal gyrus, which was shown previously to contribute to executive functions. Even though the encoding of amplitude and directional information converged and activated the same neural substrate, our data thus show that additional and partly independent mechanisms are involved in bimanual amplitude as compared to that in directional control.

Connection patterns distinguish 3 regions of human parietal cortex

Three regions of the macaque inferior parietal lobule and adjacent lateral intraparietal sulcus (IPS) are distinguished by the relative strengths of their connections with the superior colliculus, parahippocampal gyrus, and ventral premotor cortex. It was hypothesized that connectivity information could therefore be used to identify similar areas in the human parietal cortex using diffusion-weighted imaging and probabilistic tractography. Unusually, the subcortical routes of the 3 projections have been reported in the macaque, so it was possible to compare not only the terminations of connections but also their course. The medial IPS had the highest probability of connection with the superior colliculus. The projection pathway resembled that connecting parietal cortex and superior colliculus in the macaque. The posterior angular gyrus and the adjacent superior occipital gyrus had a high probability of connection with the parahippocampal gyrus. The projection pathway resembled the macaque inferior longitudinal fascicle, which connects these areas. The ventral premotor cortex had a high probability of connection with the supramarginal gyrus and anterior IPS. The connection was mediated by the third branch of the superior longitudinal fascicle, which interconnects similar regions in the macaque. Human parietal areas have anatomical connections resembling those of functionally related macaque parietal areas.

The functional organization of the intraparietal sulcus in humans and monkeys

In macaque monkeys, the posterior parietal cortex (PPC) is concerned with the integration of multimodal information for constructing a spatial representation of the external world (in relation to the macaque's body or parts thereof), and planning and executing object-centred movements. The areas within the intraparietal sulcus (IPS), in particular, serve as interfaces between the perceptive and motor systems for controlling arm and eye movements in space. We review here the latest evidence for the existence of the IPS areas AIP (anterior intraparietal area), VIP (ventral intraparietal area), MIP (medial intraparietal area), LIP (lateral intraparietal area) and CIP (caudal intraparietal area) in macaques, and discuss putative human equivalents as assessed with functional magnetic resonance imaging. The data suggest that anterior parts of the IPS comprising areas AIP and VIP are relatively well preserved across species. By contrast, posterior areas such as area LIP and CIP have been found more medially in humans, possibly reflecting differences in the evolution of the dorsal visual stream and the inferior parietal lobule. Despite interspecies differences in the precise functional anatomy of the IPS areas, the functional relevance of this sulcus for visuomotor tasks comprising target selections for arm and eye movements, object manipulation and visuospatial attention is similar in humans and macaques, as is also suggested by studies of neurological deficits (apraxia, neglect, Bálint's syndrome) resulting from lesions to this region.

Graded classes of cortical connections: quantitative analyses of laminar projections to motion areas of cat extrastriate cortex

Current hierarchical models of the cerebral cortex are mainly based on qualitative connection studies. From wheatgerm-agglutinin-horseradish peroxidase injections, we examined the laminar patterns of projections to and between the three major subdivisions of the motion-processing lateral suprasylvian (LS) complex [areas posteromedial lateral suprasylvian area (PMLS), anteromedial lateral suprasylvian (AMLS), posterolateral lateral suprasylvian area (PLLS)] of cat extrastriate cortex and of an adjoining form-processing area, 21a. We counted approximately 145,000 labelled projection cells in 20 cortical areas in 11 cats, and applied various analyses to the data, expressed as the percent supragranular layer (%SG) origin of each connection. We report two main results. (i) A wide range of %SG values was obtained, both from each individual cat and across the 163 projections examined. Nonetheless, both hierarchical and non-parametric cluster analyses of the pooled connection origins suggested the presence of three distinct laminar projection classes, constrained by graded %SG values of 0-33%, 39-69% and 76-97%. These conformed, respectively, to feedback, lateral and feedforward laminar patterns seen qualitatively in our material. (ii) Hierarchical connectivity analyses suggested that PMLS, AMLS and PLLS are ordered in a hierarchical sequence. Macaque motion areas V5/MT, MST and FST are arranged in a similar sequence, and areas at equivalent levels of the two motion hierarchies have some analogous functional specializations. Our findings provide the first objective support for the three laminar projection classes that underpin existing theoretical models of hierarchical cortical organization, and they suggest that the implementation of higher-order motion processing evolved along similar lines in the cat and monkey visual cortex.

Neural basis and recovery of spatial attention deficits in spatial neglect

The syndrome of spatial neglect is typically associated with focal injury to the temporoparietal or ventral frontal cortex. This syndrome shows spontaneous partial recovery, but the neural basis of both spatial neglect and its recovery is largely unknown. We show that spatial attention deficits in neglect (rightward bias and reorienting) after right frontal damage correlate with abnormal activation of structurally intact dorsal and ventral parietal regions that mediate related attentional operations in the normal brain. Furthermore, recovery of these attention deficits correlates with the restoration and rebalancing of activity within these regions. These results support a model of recovery based on the re-weighting of activity within a distributed neuronal architecture, and they show that behavioral deficits depend not only on structural changes at the locus of injury, but also on physiological changes in distant but functionally related brain areas.

Functional neuroimaging indicators of successful executive control in the oldest old

Attentional control, motor planning abilities, and executive cognitive functions (ECF) rapidly decline with age. In particular, older adults experience difficulty in manipulating selected motor responses in the presence of conflicting or distracting information. To examine age-related changes in the neural substrates of the attentional and motor planning components of ECF, we assessed the patterns of brain activation in 8 cognitively normal older adults (mean age 81.5) and 20 young individuals (mean age 23.0) while they responded to low and high loads of attentional demands of the Preparing to Overcome Prepotency (POP) task. In the POP task, the selection of one out of two possible motor responses in the presence of increasing attentional task loads determines the accuracy of the performance. Older individuals were slower than young adults (P < 0.001) but achieved a strikingly high accuracy similar to the young group (P = 0.2), regardless of the task load. Both groups showed a load-related fMRI signal increase in the anterior cingulate cortex (ACC), posterior parietal cortex (PPC: Brodmann areas 7 and 40), and dorsolateral prefrontal cortex (dLPFC: Brodmann areas 9, 45, and 46) bilaterally. Compared to young individuals, older adults had lower activation in dLPFC (Brodmann areas 9, 45, and 46: P = 0.007, P = 0.043, and P = 0.040) and Brodmann area 7, P = 0.002. Activation in Brodmann areas 40 and ACC was similar in the two groups (P > 0.05). Among older adults, the most successful performers were those who responded to increasing task loads with greater activation in PPC (Brodmann area 40), despite lower dLPFC activation. Older adults who are able to perform executive control tasks as well as young adults, also seem to implement speed-accuracy trade-off strategies which may rely on increased parietal activation.

The role of anterior cingulate cortex and precuneus in the coordination of motor behaviour

Behavioral studies in humans have shown that bimanual coordination imposes specific demands on the central nervous system that exceed unimanual task control. In the present study we used functional magnetic resonance imaging to investigate the neural correlate of this additional coordination effort, i.e. regions responding more strongly to bimanual movements than inferred from summing up the responses to the unimanual subtasks. Subjects were scanned while performing movements along different directions, either uni- or bimanually. During the bimanual condition, trajectories of movement of the left and right hand were spatially incompatible, such that additional effort was required to break away from intrinsically favored mirror-movements and to integrate movements of both limbs into a new spatial pattern. Our main finding was that the execution of spatially complex bimanual coordination as compared with the unimanual subtasks activated the anterior cingulate cortex (posterior part) as well as the dorso-anterior precuneus. We hypothesize that the anterior cingulate exerts its modulatory effect on other motor areas, such as the primary motor cortex and the supplementary motor area, in order to suppress intrinsically favored coordination tendencies. Conversely, the precuneus is likely to be involved in shifting attention between different locations in space, which was necessary for monitoring the trajectories of the left and right wrist when both limbs moved in parallel. Our findings suggest that the coordination effort during bimanual and perhaps other modes of coordinated behavior is mediated by regions contributing to higher order functions, which form an interface between cognition and action.

Tactile discrimination of grating orientation: fMRI activation patterns

Grating orientation discrimination is employed widely to test tactile spatial acuity. We used functional magnetic resonance imaging (fMRI) to investigate the neural circuitry underlying performance of this task. Two studies were carried out. In the first study, an extensive set of parietal and frontal cortical areas was activated during covert task performance, relative to a rest baseline. The active regions included the postcentral sulcus bilaterally and foci in the left parietal operculum, left anterior intraparietal sulcus, and bilateral premotor and prefrontal cortex. The second study examined selective recruitment of cortical areas during discrimination of grating orientation (a task with a macrospatial component) compared to discrimination of grating spacing (a purely microspatial task). The foci activated on this contrast were in the left anterior intraparietal sulcus, right postcentral sulcus and gyrus, left parieto-occipital cortex, bilateral frontal eye fields, and bilateral ventral premotor cortex. These findings not only confirm and extend previous studies of the neural processing underlying grating orientation discrimination, but also demonstrate that a distributed network of putatively multisensory areas is involved.

Mapping multiple visual areas in the human brain with a short fMRI sequence

It is a fundamental insight of neuroscience that the cerebral cortex is divided into spatially separated and functionally distinct areas. In this study, we tried to map a large number of visual areas in individual subjects passively viewing a simple stimulus sequence during functional magnetic resonance imaging (fMRI) at 1.5 T. The blocked stimulus sequence contrasted static object photographs with video takes of movement through natural indoor and outdoor scenes, alternated with a control fixation task. Two runs of the 5-min sequence sufficed to invoke 29 distinguishable activations, 16 (13 bilateral) of which were observed in all 10 participants. At the ventral side, object responsive activations were organized along the lateral occipital-temporal surface and near the collateral and occipital-temporal sulci. The latter activations, corresponding to the lateral occipital complex, showed a different activation profile from those near the collateral sulcus, most likely corresponding to the color constancy areas V4/V8-V4alpha. A potentially new fusiform object area was seen in 6 subjects, even more anterior than the parahippocampal place area. At the dorsal side, consistent activations were mainly related to motion stimuli and included the well-known areas V3a, VIPS, POIPS, hV5+, STS and the cingulate sulcus. There was consistent activation in the parietal-occipital sulcus, containing the areas V6a and V6. In addition, all subjects showed activation in the superior-anterior precuneus. Thus, the short stimulus sequence robustly invoked multiple visual areas and can be used to map the organization of the visual system in normal and brain-damaged individuals.

Low-dose estradiol alters brain activity

Although several studies have examined the effects of estrogen replacement therapy (ERT) on neural activity associated with tasks of learning and memory, no study has examined such effects on a sustained attention task. This study examined the effect of low-dose estrogen replacement therapy on hemodynamic activity elicited by a visual three-stimulus oddball task recorded using event-related functional magnetic resonance imaging (fMRI). Participants included 16 women between the ages of 73 and 84 who were part of a randomized controlled double-blind study to evaluate the effect of an ultralow dose micronized estradiol on bone. No significant differences in behavioral performance were found with ERT. However, there was evidence that ERT group participants had both reductions and increases in the amplitude of hemodynamic response in a variety of subcortical and cortical brain regions. These included regions involved in perception and attention such as the occipital and parietal lobes, motor cortex, anterior cingulate and prefrontal cortex. These findings suggest that estrogen may facilitate the efficiency of brain function during the performance of sustained attention tasks in post-menopausal elderly women.

A special role for numbers in working memory? An fMRI study

Although numbers carry averbal semantics (i.e., magnitude), they are often utilized in verbal Working Memory (vWM) tasks. However, vWM is thought to rely on a purely phonological code. Here, we tested the influence of (a) averbal semantics and (b) different tasks on performance in a vWM context by examining stimulus and task-specific variation of activity in the horizontal parts of the intraparietal sulcus (hIPS). The hIPS has previously been shown to subserve magnitude processing modulated by (a) specific stimuli and (b) specific tasks. Two variants of an n-back paradigm (comparison and identity match tasks) utilizing letters and numbers as stimulus material at different levels of vWM load were administered in 16 participants. Behavioral and functional imaging data reveal stimulus-specific modulation of activity in the hIPS suggesting a semantic influence of numbers. In the identity match task, numbers induced additional hIPS activation compared to letters while letters never induced additional hIPS activation when compared to numbers. Letters as compared to numbers only induced additional hIPS activation in the comparison task. These results question the assumption of a purely phonological code in vWM because hIPS activation subserving magnitude processing is modulated by stimulus semantics and task demands.

Components of bottom-up gaze allocation in natural images

Recent research [Parkhurst, D., Law, K., & Niebur, E., 2002. Modeling the role of salience in the allocation of overt visual attention. Vision Research 42 (1) (2002) 107-123] showed that a model of bottom-up visual attention can account in part for the spatial locations fixated by humans while free-viewing complex natural and artificial scenes. That study used a definition of salience based on local detectors with coarse global surround inhibition. Here, we use a similar framework to investigate the roles of several types of non-linear interactions known to exist in visual cortex, and of eccentricity-dependent processing. For each of these, we added a component to the salience model, including richer interactions among orientation-tuned units, both at spatial short range (for clutter reduction) and long range (for contour facilitation), and a detailed model of eccentricity-dependent changes in visual processing. Subjects free-viewed naturalistic and artificial images while their eye movements were recorded, and the resulting fixation locations were compared with the models' predicted salience maps. We found that the proposed interactions indeed play a significant role in the spatiotemporal deployment of attention in natural scenes; about half of the observed inter-subject variance can be explained by these different models. This suggests that attentional guidance does not depend solely on local visual features, but must also include the effects of interactions among features. As models of these interactions become more accurate in predicting behaviorally-relevant salient locations, they become useful to a range of applications in computer vision and human-machine interface design.

Cortical regions involved in eye movements, shifts of attention, and gaze perception

Human vision is an active process that involves shifting attention across the visual scene, with or without moving the eyes. Such shifts of attention can be generated at will (endogenously) or be triggered automatically, i.e., generated in response to exogenous stimuli including socially relevant cues such as someone else's gaze. What are the common and distinct brain mechanisms involved in these processes? To address this question, we carried out a quantitative effect-location meta-analysis of 59 brain-imaging experiments whose results were published using standardized coordinates. For each condition of interest, namely voluntary and visually triggered eye movements, voluntary and visually triggered (covert) shifts of attention, and perception of someone else's gaze, we computed activation likelihood estimation (ALE) maps. Those maps represent at each voxel of the brain the probability of reporting a signal change related to the condition of interest. For eye movements, this analysis confirmed the spatial location of the frontal eye fields, supplementary eye fields, and parietal saccade-related regions. The map of covert shifts of attention demonstrated highest similarity with the map of saccadic eye movements. Gaze perception showed common activation likelihood with the other conditions in the right intraparietal sulcus and in the lateral precentral gyrus. It demonstrated more similarity with the reflexive than with the voluntary saccades and shifts of attention. We propose that a core network of frontoparietal and temporal brain regions is recruited when we shift the focus of our attention with or without eye movements in response to the appearance of a visual target, as well as when we see someone else shift his or her gaze.

Frontoparietal Control of Spatial Attention and Motor Intention in Human EEG

Relations between spatial attention and motor intention were investigated by means of an EEG potential elicited by shifting attention to a location in space as well as by the selection of a hand for responding. High-density recordings traced this potential to a common frontoparietal network activated by attentional orienting and by response selection. Within this network, parietal and frontal cortex were activated sequentially, followed by an anterior-to-posterior migration of activity culminating in the lateral occipital cortex. Based on temporal and polarity information provided by EEG, we hypothesize that the frontoparietal activation, evoked by directional information, updates a task-defined preparatory state by deselecting or inhibiting the behavioral option competing with the cued response side or the cued direction of attention. These results from human EEG demonstrate a direct EEG manifestation of the frontoparietal attention network previously identified in functional imaging. EEG reveals the time-course of activation within this network and elucidates the generation and function of associated directing-attention EEG potentials. The results emphasize transient activation and a decision-related function of the frontoparietal attention network, contrasting with the sustained preparatory activation that is commonly inferred from neuroimaging.

From monkeys to humans: what do we now know about brain homologies?

Different primate species, including humans, have evolved by a repeated branching of lineages, some of which have become extinct. The problem of determining the relationships among cortical areas within the brains of the surviving branches (e.g. humans, macaque monkeys, owl monkeys) is difficult for several reasons. First, evolutionary intermediates are missing, second, measurement techniques are different in different primate species, third, species differ in body size, and fourth, brain areas can duplicate, fuse, or reorganize between and within lineages.

Interactions between number and space in parietal cortex

Since the time of Pythagoras, numerical and spatial representations have been inextricably linked. We suggest that the relationship between the two is deeply rooted in the brain's organization for these capacities. Many behavioural and patient studies have shown that numerical-spatial interactions run far deeper than simply cultural constructions, and, instead, influence behaviour at several levels. By combining two previously independent lines of research, neuroimaging studies of numerical cognition in humans, and physiological studies of spatial cognition in monkeys, we propose that these numerical-spatial interactions arise from common parietal circuits for attention to external space and internal representations of numbers.

Distribution of Activity Across the Monkey Cerebral Cortical Surface, Thalamus and Midbrain during Rapid, Visually Guided Saccades

To examine the distribution of visual and oculomotor activity across the macaque brain, we performed functional magnetic resonance imaging (fMRI) on awake, behaving monkeys trained to perform visually guided saccades. Two subjects alternated between periods of making saccades and central fixations while blood oxygen level dependent (BOLD) images were collected [3 T, (1.5 mm)3 spatial resolution]. BOLD activations from each of four cerebral hemispheres were projected onto the subjects' cortical surfaces and aligned to a surface-based atlas for comparison across hemispheres and subjects. This surface-based analysis revealed patterns of visuo-oculomotor activity across much of the cerebral cortex, including activations in the posterior parietal cortex, superior temporal cortex and frontal lobe. For each cortical domain, we show the anatomical position and extent of visuo-oculomotor activity, including evidence that the dorsolateral frontal activation, which includes the frontal eye field (on the anterior bank of the arcuate sulcus), extends anteriorly into posterior principal sulcus (area 46) and posteriorly into part of dorsal premotor cortex (area 6). Our results also suggest that subcortical BOLD activity in the pulvinar thalamus may be lateralized during voluntary eye movements. These findings provide new neuroanatomical information as to the complex neural substrates that underlie even simple goal-directed behaviors.

A functional MRI study of automatic movements in patients with Parkinson's disease

Patients with Parkinson's disease have great difficulty performing learned movements automatically. The neural contribution to the problem has not been identified. In the current study, we used functional magnetic resonance imaging (fMRI) to investigate the underlying neural mechanisms of movement automaticity in Parkinson's disease patients. Fifteen patients with Parkinson's disease were recruited. Three patients were finally excluded because they could not achieve automaticity. The remaining 12 patients were aged from 52 to 67 years, with a mean age of 61.2 years. Controls included 14 age-matched normal subjects. The subjects were asked to practise four tasks, including two self-initiated, self-paced sequences of finger movements with different complexity until they could perform the tasks automatically. Two dual tasks were used to evaluate automaticity. For dual tasks, subjects performed a visual letter-counting task simultaneously with the sequential movements. Twelve normal subjects performed all sequences automatically. All patients performed sequences correctly; 12 patients could perform the simpler sequence automatically; and only 3 patients could perform the more complex sequence automatically. fMRI results showed that for both groups, sequential movements activated similar brain regions before and after automaticity was achieved. No additional activity was observed in the automatic condition. In normal subjects, many areas had reduced activity at the automatic stage, whereas in patients, only the bilateral superior parietal lobes and left insular cortex were less activated. Patients had greater activity in the cerebellum, premotor area, parietal cortex, precuneus and prefrontal cortex compared with normal subjects while performing automatic movements. We conclude that Parkinson's disease patients can achieve automaticity after proper training, but with more difficulty. Our study is the first to demonstrate that patients with Parkinson's disease require more brain activity to compensate for basal ganglia dysfunction in order to perform automatic movements.

A functional MRI study of preparatory signals for spatial location and objects

We investigated preparatory signals for spatial location and objects in normal observers using functional magnetic resonance imaging (fMRI). Activity for attention-directing cues was separated from activity for subsequent test arrays containing the target stimulus. Subjects were more accurate in discriminating a target face among distracters when they knew in advance its location (spatial directional cue), as compared to when the target could randomly appear at one of two locations (spatial neutral cue), indicating that the spatial cue was used. Spatially specific activations occurred in a region at the intersection of the ventral intraparietal sulcus and transverse occipital sulcus (vIPS-TOS), which showed significantly stronger activation for rightward- than leftward-directing cues, while other fronto-parietal areas were activated by the cue but did not show spatial specificity. In visual cortex, activity was weak or absent in retinotopic occipital regions following attention-directing cues and this activity was not spatially specific. In a separate task, subject discriminated a target outdoor scene among distracters after the presentation of spatial neutral cues. There was no significant difference in dorsal frontoparietal activity during the face versus scene discrimination task. Also, there was only weak evidence for selective preparatory activity in ventral object-selective regions, although the activation of these regions to the subsequent test array did depend upon which discrimination (face or place) was performed. We conclude first that under certain circumstances, spatial cues that produce strong behavioral effects may modulate parietal-occipital regions in a spatially specific manner without producing similar modulations in retinotopic occipital regions. Second, attentional modulations of object-selective regions in temporal-occipital cortex can occur even though preparatory object-selective modulations of those regions are absent or weak.