Mental rotation and object categorization share a common network of prefrontal and dorsal and ventral regions of posterior cortex

Visual object cognition precedes but also temporally overlaps mental rotation

Two-dimensional, mental rotation of alphanumeric characters and geometric figures is related to linear increases in parietal negativity between 400 and 800 ms as rotation increases, similar to linear increases with rotation in response times. This suggests that the frontoparietal networks implicated in mental rotation are engaged after 400 ms. However, the time course of three-dimensional object mental rotation using the classic Shepard-Metzler task has not been studied, even though this is one of the most commonly used versions in behavioral and neuroimaging work. Using this task, this study replicated a prior neuroimaging version using event-related potentials. Results confirmed linear mental rotation effects on performance and parietal negativity. In addition, a frontocentral N350 complex that indexes visual object cognition processes was more negative with mental rotation and showed linear trends at frontopolar sites from 200 to 700 ms and centrofrontal sites from 400 to 500 ms. The centrofrontal negativity has been implicated in object working memory processes in ventrolateral prefrontal and occipitotemporal areas. The frontopolar N350 has been implicated in processes that compute the spatial relations among parts of objects to resolve visual differences between object representations and enable an accurate cognitive decision involving a network of ventrocaudal intraparietal, ventral premotor, and inferotemporal cortices. Overall, the time course indicates that visual object cognition processes precede (200-500 ms) but also overlap the initial phase of mental rotation (500-700 ms) indexed by parietal negativity.

Dynamic changes in the mental rotation network revealed by pattern recognition analysis of fMRI data

We investigated the temporal dynamics and changes in connectivity in the mental rotation network through the application of spatio-temporal support vector machines (SVMs). The spatio-temporal SVM [Mourao-Miranda, J., Friston, K. J., et al. (2007). Dynamic discrimination analysis: A spatial-temporal SVM. Neuroimage, 36, 88-99] is a pattern recognition approach that is suitable for investigating dynamic changes in the brain network during a complex mental task. It does not require a model describing each component of the task and the precise shape of the BOLD impulse response. By defining a time window including a cognitive event, one can use spatio-temporal fMRI observations from two cognitive states to train the SVM. During the training, the SVM finds the discriminating pattern between the two states and produces a discriminating weight vector encompassing both voxels and time (i.e., spatio-temporal maps). We showed that by applying spatio-temporal SVM to an event-related mental rotation experiment, it is possible to discriminate between different degrees of angular disparity (0 degrees vs. 20 degrees , 0 degrees vs. 60 degrees , and 0 degrees vs. 100 degrees ), and the discrimination accuracy is correlated with the difference in angular disparity between the conditions. For the comparison with highest accuracy (0 degrees vs. 100 degrees ), we evaluated how the most discriminating areas (visual regions, parietal regions, supplementary, and premotor areas) change their behavior over time. The frontal premotor regions became highly discriminating earlier than the superior parietal cortex. There seems to be a parcellation of the parietal regions with an earlier discrimination of the inferior parietal lobe in the mental rotation in relation to the superior parietal. The SVM also identified a network of regions that had a decrease in BOLD responses during the 100 degrees condition in relation to the 0 degrees condition (posterior cingulate, frontal, and superior temporal gyrus). This network was also highly discriminating between the two conditions. In addition, we investigated changes in functional connectivity between the most discriminating areas identified by the spatio-temporal SVM. We observed an increase in functional connectivity between almost all areas activated during the 100 degrees condition (bilateral inferior and superior parietal lobe, bilateral premotor area, and SMA) but not between the areas that showed a decrease in BOLD response during the 100 degrees condition.

Role of a lateralized parietal-basal ganglia circuit in hierarchical pattern perception: evidence from Parkinson's disease

The role of corticostriatal circuits in hierarchical pattern perception was examined in Parkinson's disease. The hypothesis was tested that patients with right-side onset of motor symptoms (RPD, left hemisphere dysfunction) would be impaired at local level processing because the left posterior temporoparietal junction (TP) emphasizes processing of local information. By contrast, left-side onset patients (LPD; right hemisphere dysfunction) would show impaired global processing because right TP emphasizes global processing. Participants identified targets at local or global levels without and with attention biased toward those levels. Despite normal attentional control between levels, LPD patients showed a single dissociation, demonstrating abnormal global level processing under all conditions, whereas RPD patients showed abnormal local level processing mainly when attention was biased toward the local level. These findings link side of motor symptom onset to visuospatial cognitive abilities that depend upon the contralateral TP, highlighting that side of onset can predict visuospatial impairments, and provide evidence that an inferior parietal-basal ganglia pathway involving the caudate head and the hemispherically asymmetrical TP region is necessary for hierarchical pattern perception.

Sex influences on the neurobiology of learning and memory

In essentially every domain of neuroscience, the generally implicit assumption that few, if any, meaningful differences exist between male and female brain function is being challenged. Here we address how this development is influencing studies of the neurobiology of learning and memory. While it has been commonly held that males show an advantage on spatial tasks, and females on verbal tasks, there is increasing evidence that sex differences are more widespread than previously supposed. Differing performance between the sexes have been observed on a number of common learning tasks in both the human and animal literature, many neither purely spatial nor verbal. We review sex differences reported in various areas to date, while attempting to identify common features of sexually dimorphic tasks, and to place these differences in a neurobiological context. This discussion focuses on studies of four classes of memory tasks for which sex differences have been frequently reported: spatial, verbal, autobiographical, and emotional memory. We conclude that the female verbal advantage extends into numerous tasks, including tests of spatial and autobiographical abilities, but that a small but significant advantage may exist for general episodic memory. We further suggest that for some tasks, stress evokes sex differences, which are not normally observed, and that these differences are mediated largely by interactions between stress and sex hormones.

Combining path analysis with time-resolved functional magnetic resonance imaging: the neurocognitive network underlying mental rotation

There is strong evidence to suggest that the complex cognitive process underlying mental rotation does not have a discrete neural correlate, but is represented as a distributed neural system. Although the neuroanatomical nodes of this so-called rotation network are well established, there is as yet little empirical evidence to indicate how these nodes interact during task performance. Using an optimized, event-related paradigm, this study aimed to test a previously proposed hypothetical neurocognitive network for mental rotation in female subjects with path analysis, and to examine changes in effective connections across different levels of task difficulty. Path analysis was carried out in combination with a time-resolved functional magnetic resonance imaging (fMRI) analysis in order to relate the observed changes on the network level to changes in specific temporal characteristics of the hemodynamic response function on the level of individual neuroanatomical nodes. Overall, it was found that the investigated sequential model did not provide an adequate fit to the data and that a model with parallel information processing was superior to the serial model. This finding challenges traditional cognitive models describing the complex cognitive process underlying mental rotation by a set of sequentially organized, functionally distinct processing stages. It was further demonstrated that the observed in interregional effective connectivity changes with the level of task demand. These changes were directly related to the time course of the experimental paradigm. The results of path analysis in fMRI should therefore only be interpreted in the light of a specific experimental design and should not be considered as general indicators of effective connections.

Where vision meets memory: prefrontal-posterior networks for visual object constancy during categorization and recognition

Objects seen from unusual relative to more canonical views require more time to categorize and recognize, and, according to object model verification theories, additionally recruit prefrontal processes for cognitive control that interact with parietal processes for mental rotation. To test this using functional magnetic resonance imaging, people categorized and recognized known objects from unusual and canonical views. Canonical views activated some components of a default network more on categorization than recognition. Activation to unusual views showed that both ventral and dorsal visual pathways, and prefrontal cortex, have key roles in visual object constancy. Unusual views activated object-sensitive and mental rotation (and not saccade) regions in ventrocaudal intraparietal, transverse occipital, and inferotemporal sulci, and ventral premotor cortex for verification processes of model testing on any task. A collateral-lingual sulci "place" area activated for mental rotation, working memory, and unusual views on correct recognition and categorization trials to accomplish detailed spatial matching. Ventrolateral prefrontal cortex and object-sensitive lateral occipital sulcus activated for mental rotation and unusual views on categorization more than recognition, supporting verification processes of model prediction. This visual knowledge framework integrates vision and memory theories to explain how distinct prefrontal-posterior networks enable meaningful interactions with objects in diverse situations.