Frontal cortex atrophy predicts cognitive impairment in multiple sclerosis

The association between regional measures of cortical atrophy and neuropsychological (NP) dysfunction was studied in 35 multiple sclerosis (MS) patients. Patients underwent neurological examination, MRI, and NP testing. Blind quantitative MRI analysis yielded total T(2) lesion area (TLA) and third ventricle width (3VW). Cortical atrophy, rated by blind visual inspection, was more extensive in superior frontal and parietal cortices than in other regions. No MRI measures were correlated with depression scores. TLA and 3VW were significantly correlated with each NP test. Cortical atrophy measures for bilateral superior frontal cortex were retained in regression models predicting impairments in verbal learning, spatial learning, attention, and conceptual reasoning. The authors conclude that cerebral atrophy predicts NP impairment while accounting for the influence of TLA or 3VW. Regions of cortex most susceptible to atrophic and cognitive changes in MS are the right and left superior frontal lobes.

Addiction denial and cognitive dysfunction: a preliminary investigation

This study explored the proposition that denial of addiction is often more a product of cognitive failure due to cerebral dysfunction than an emotion-driven rejection of the truth. Forty-four subjects were studied in an inpatient alcohol rehabilitation program. Denial was defined as the proportion of standardized denial-related treatment goals established at admission that remained unachieved at discharge. Cognitive deficiencies were identified through neuropsychological assessments. Persistent denial was significantly correlated with greater impairment of executive function, verbal memory, visual inference, and mental speed.

Top-down effects can modify the initially stimulus-driven auditory organization

We recorded event-related potentials (ERPs) and magnetic fields (ERFs) of the human brain to determine whether top-down control could modulate the initial organization of sound representations in the auditory cortex. We presented identical sound stimulation and manipulated top-down processes by instructing participants to either ignore the sounds (Ignore condition), to detect pitch changes (Attend-pitch condition), or to detect violations of a repeating tone pattern (Attend-pattern condition). The ERP results obtained in the Attend-pattern condition dramatically differed from those obtained with the other two task instructions. The magnetoencephalogram (MEG) findings were fully compatible, showing that the neural populations involved in detecting pattern violations differed from those involved in detecting pitch changes. The results demonstrate a top-down effect on the sound representation maintained in auditory cortex.

A qualitative and quantitative analysis of rhythmic activities during a mental task and sleep spindles

The frequency, configuration, and distribution of sleep spindles are similar to some of the rhythmic activities seen during task performance. In the present study, the relationship between rhythmic activities during sleep and arithmetic addition was investigated in male university students with (n = 10) and without (n = 10) frontal midline theta activity (Fmtheta). Electroencephalograms (EEGs) during addition in both groups were compared at frontal and central areas on three consecutive days. Polysomnograms were recorded at the same regions on four consecutive nights for each group. The amount of theta rhythm during a mental task (Fmtheta) and in nocturnal sleep at Fz and Cz electrodes was greater for the Fmtheta group than for the non-Fmtheta group, while the amount of beta rhythm at both sites was smaller in the Fmtheta group than in the non-Fmtheta group. There were no differences between the groups in the amount of alpha rhythm at either site. The frequency of alpha rhythm at Fz and Cz in both situations was slower for the Fmtheta group than for the non-Fmtheta group, but there were no differences in the frequency of theta and beta rhythms between the groups at either site. These results suggest that rhythmic activities during a mental task and in sleep may correlate with each other.

Event-related potentials during discourse-level semantic integration of complex pictures

This study examined event-related potentials (ERPs) elicited in response to semantic processing of non-verbal stories. ERPs were recorded from 29 scalp electrodes on 16 participants while they viewed series of complex gray-scale pictures, each of which relayed a simple story. The final picture of each story was either congruous or incongruous with the preceding context. Participants made delayed meaningfulness judgments for each story. Averaged ERPs time-locked to the onset of the final picture were more negative for incongruous than congruous pictures. Two distinct components were sensitive to congruency. The first component peaked at approximately 325 ms (N300) and was distributed over central and frontal sites. The second component peaked at approximately 500 ms and also had a centro-frontal maximum but was more widespread than the earlier component (anterior N400). The distinct scalp topographies of these two negativities provide strong evidence that the N300 and N400 are separate and distinguishable components. Furthermore, the presence of the N300 in this exclusively pictorial task suggests that the N300 is specific to the semantic processing of non-verbal stimuli and is not due to linguistic mediation. This study also revealed that the N400 can be modulated by discourse-level coherence manipulations with pictures. Finally, the different patterns of ERP effects observed during the semantic processing of verbal and non-verbal information suggest that non-identical neuronal sources, and thus non-identical representational systems, are accessed by these different types of materials. These findings strongly support at least partial modularity of semantic representations and processing mechanisms in the human brain.

The interplay of meaning, sound, and syntax in sentence production

A discussion of modularity in language production processes, with special emphasis on processes for retrieving words and building syntactic structures for a to-be-uttered sentence, is presented. The authors' 1st goal was to assess the extent to which information processing is encapsulated between different processing stages. In particular, they assessed whether the input from one processing stage to the next is minimal and whether the flow of information in the system is strictly unidirectional. On the basis of the reviewed evidence, they conclude that both assumptions have to be revised. Their 2nd goal was to propose an altemative framework that does not assume strict encapsulation but that maintains multiple levels of integration for production.

The relationship between rhythmic activities during a mental task and sleep spindles: a correlative analysis

In a previous study, we suggested that the characteristics of theta, alpha, and beta rhythms during a mental task were similar to those during sleep. Building upon the previous data, correlations between rhythmic activities during a mental task and during sleep were investigated in the present study. Patterns of correlation and no correlation between rhythmic activities during the mental task were similar to those during sleep for subjects with and without frontal midline theta (Fmtheta) activity. In the Fmtheta group, there were no correlations between rhythmic activities in the two situations, while in the non-Fmtheta subjects, theta and alpha rhythms showed a positive correlation with one another, and theta and beta rhythms correlated negatively during sleep. In both groups, there were many correlations between rhythmic activities during the mental task and those in Sleep Stage 2, while there were few correlations between rhythmic activities during the mental task and those in other sleep stages. These results suggest that the mechanism generating rhythmic activities during the appearance of rhythmic activities induced by a mental task may be closely related to those of rhythmic activities during sleep, and that the membrane potentials in reticular thalamic (RE) neurons during the appearance of rhythmic activities induced by a mental task may be nearly equivalent to that in Sleep Stage 2, and that the correlation pattern between the rhythmic activities in each group may be well explained by the appearance pattern of each rhythm in the previous report.

Naive causal understanding of valenced behaviors and its implications for social information processing

People bring to bear on their understanding of others' behaviors naive theories of the causes of valenced behaviors. Generally, positive behaviors are understood to be caused by social demands, whereas negative behaviors are understood to be caused by people's dispositions. Various research findings are reviewed in support of the idea that people possess such naive theories. The analysis is extended to establish how these sense-making tendencies affect the manner in which people approach and process information about others. A second set of studies is reviewed in support of these implications for person perception. Comparisons to other models of social inference are considered, implications of the frame-work are examined, and the framework is situated within a general model of the attribution process.

Access to information in working memory: exploring the focus of attention

Participants memorized briefly presented sets of digits, a subset of which had to be accessed as input for arithmetic tasks (the active set), whereas another subset had to be remembered independently of the concurrent task (the passive set). Latencies for arithmetic operations were a function of the setsize of active but not passive sets. Object-switch costs were observed when successive operations were applied to different digits within an active set. Participants took 2 s to encode a passive set so that it did not affect processing latencies (Experiment 2). The results support a model distinguishing 3 states of representations in working memory: the activated part of long-term memory, a capacity limited region of direct access, and a focus of attention.

Can't shake that feeling: event-related fMRI assessment of sustained amygdala activity in response to emotional information in depressed individuals

BACKGROUND

Previous research suggests that depressed individuals engage in prolonged elaborative processing of emotional information. A computational neural network model of emotional information processing suggests this process involves sustained amygdala activity in response to processing negative features of information. This study examined whether brain activity in response to emotional stimuli was sustained in depressed individuals, even following subsequent distracting stimuli.

METHODS

Seven depressed and 10 never-depressed individuals were studied using event-related functional magnetic resonance imaging during alternating 15-sec emotional processing (valence identification) and non-emotional processing (Sternberg memory) trials. Amygdala regions were traced on high-resolution structural scans and co-registered to the functional data. The time course of activity in these areas during emotional and non-emotional processing trials was examined.

RESULTS

During emotional processing trials, never-depressed individuals displayed amygdalar responses to all stimuli, which decayed within 10 sec. In contrast, depressed individuals displayed sustained amygdala responses to negative words that lasted throughout the following non-emotional processing trials (25 sec later). The difference in sustained amygdala activity to negative and positive words was moderately related to self-reported rumination.

CONCLUSIONS

Results suggest that depression is associated with sustained activity in brain areas responsible for coding emotional features.

Effects of picture repetition on induced gamma band responses, evoked potentials, and phase synchrony in the human EEG

Repeated experience with an object due to prior exposure to that object is commonly referred to as perceptual or repetition priming. One possible neuronal mechanism for repetition priming is 'repetition suppression' within a cell assembly coding the stimulus. Recently, induced gamma band responses (GBRs) were discussed as a possible physiological correlate of activity in such a cell assembly. The present EEG study was designed to investigate the modulation of induced GBRs when line drawings were presented either once or consecutively two or three times. Results showed a broad distribution of spectral gamma power and synchrony after initial picture presentation. Repeated presentations of the same picture led to a decrease of induced gamma power and less synchronized activity between distant electrode sites. The decrease of induced GBRs and synchrony after repeated picture presentations may be linked to a 'neural savings' mechanism within a cell assembly representing an object. Furthermore, the visual evoked potential, which was modulated by priming, showed a topographically different distribution compared to induced GBRs.

The integration of neurology, psychiatry, and neuroscience in the 21st century

OBJECTIVE

This article examines the historical basis for the divergence of neurology and psychiatry over the past century and discusses prospects for a rapprochement and potential convergence of the two specialties in the next century.

METHOD

The author presents a brief historical overview of developments in neurology and psychiatry from the late 19th century. The histories of research and prevailing scientific opinion on two neuropsychiatric disorders, Alzheimer's disease and Tourette's syndrome, are compared to illustrate the effects of viewing a disease process from, respectively, the neurologic/organic and psychiatric/functional perspectives.

RESULTS

Research on Alzheimer's disease, because of its early pathologic demonstration, moved rapidly toward identification of associated synaptic abnormalities and genetic mutations. In Tourette's syndrome, the absence of evident brain pathology resulted in vacillation between organic and functional explanations and persistent controversy about the nature of the illness.

CONCLUSIONS

Neurology and psychiatry have, for much of the past century, been separated by an artificial wall created by the divergence of their philosophical approaches and research and treatment methods. Scientific advances in recent decades have made it clear that this separation is arbitrary and counterproductive. Neurologic and psychiatric research are moving closer together in the tools they use, the questions they ask, and the theoretical frameworks they employ. The interests of neurology and psychiatry converge within the framework of modern neuroscience. Further progress in understanding brain diseases and behavior demands fuller collaboration and integration of these fields. Leaders in academic medicine and science must work to break down the barriers between disciplines.

Self-organization in the basal ganglia with modulation of reinforcement signals

Self-organization is one of fundamental brain computations for forming efficient representations of information. Experimental support for this idea has been largely limited to the developmental and reorganizational formation of neural circuits in the sensory cortices. We now propose that self-organization may also play an important role in short-term synaptic changes in reward-driven voluntary behaviors. It has recently been shown that many neurons in the basal ganglia change their sensory responses flexibly in relation to rewards. Our computational model proposes that the rapid changes in striatal projection neurons depend on the subtle balance between the Hebb-type mechanisms of excitation and inhibition, which are modulated by reinforcement signals. Simulations based on the model are shown to produce various types of neural activity similar to those found in experiments.

Information processing speed and sentence comprehension in Parkinson's disease

This study tests the hypothesis that sentence comprehension difficulty in Parkinson's disease (PD) is related in part to altered information processing speed that plays a crucial role in grammatical processing. The authors measured information processing speed in 32 PD patients without dementia using a lexical list-priming paradigm in which the interstimulus interval (ISI) between the prime and the target varied. Sentence comprehension accuracy was also assessed in 22 of these patients. Sentence comprehension accuracy for object-relative center-embedded sentences was impaired in a subgroup of PD patients. This subgroup of PD patients primed at an abnormally long ISI. Similarly, only PD patients who primed at a long ISI had greater difficulty understanding sentences with an object-relative clause than a subject-relative clause. Findings suggest that slowed information processing speed contributes to sentence comprehension difficulty in PD.

Evidence for intact semantic representations in patients with frontal lobe lesions

Patients with frontal lobe lesions and control participants were assessed on 2 tests of semantic knowledge. In the triadic comparison task, participants were shown all possible triplets of 12 animal names and judged which 2 of each triplet were most alike. In the ordered similarity task, participants rank ordered animals in terms of their similarity to a target animal. For both tasks, semantic structure--derived from multidimensional scaling techniques--revealed similar representations in patients with frontal lobe lesions and control participants. Additional pathfinder analyses also produced networks that did not differ between groups. These patients exhibited intact semantic knowledge despite deficits on tests of free recall and verbal fluency that involved the same semantic category and exemplars. Thus, intact representation of semantic knowledge in frontal patients stands in contrast to their marked deficits in strategic retrieval of semantic knowledge.

Spatial imagery in deductive reasoning: a functional MRI study

Various cognitive theories aim to explain human deductive reasoning: (1) mental logic theories claim syntactic language-based proofs of derivation, (2) the mental model theory proposes cognitive processes of constructing and manipulating spatially organized mental models, and (3) imagery theories postulate that such abilities are based on visual mental images. To explore the neural substrates of human deductive reasoning, we examined BOLD (blood oxygen level dependent) contrasts of twelve healthy participants during relational and conditional reasoning with whole-brain functional magnetic resonance imaging (fMRI). The results indicate that, in the absence of any correlated visual input, reasoning activated an occipitoparietal-frontal network, including parts of the prefrontal cortex (Brodmann's area, BA, 6, 9) and the cingulate gyrus (BA 32), the superior and inferior parietal cortex (BA 7, 40), the precuneus (BA 7), and the visual association cortex (BA 19). In the discussion, we first focus on the activated occipito-parietal pathway that is well known to be involved in spatial perception and spatial working memory. Second, we briefly relate the activation in the prefrontal cortical areas and in the anterior cingulate gyrus to other imaging studies on higher cognitive functions. Finally, we draw some general conclusions and argue that reasoners envisage and inspect spatially organized mental models to solve deductive inference problems.

Neural activation during an explicit categorization task: category- or feature-specific effects?

Previous lesion-deficit and functional imaging studies have suggested that there are distinct category-specific regions within the human brain. Using functional magnetic resonance imaging, we tested this claim with a task in which participants decided if two items, represented by words, were members of the same category. Signal changes detected for all pairs of items that were from the same category and for tool pairs were found in rostromedial BA 6, rostral cingulate, and at the BA 6/44 and BA 45/46 junctions. Activation was seen in BA 6 and the left BA 6/44 junction for fruits and vegetables pairs and only in rostromedial BA 6 for animal pairs. The common signal changes in the frontal lobes (BA 6/44) for the categories of fruits and vegetables and tools suggest that this region may be organized in a feature-specific, as opposed to a category-specific, manner.

Measurements of brain activity complexity for varying mental loads

Using functional magnetic resonance imaging, we investigate the variation in dynamical complexity of human brain activity for different mental loads. Our experiments measured the activity of ten subjects under three experimental conditions: a rest condition, a periodic task of finger opposition, and a task of finger opposition alternated with mathematical serial calculation. We used the correlation dimension to gauge the spatiotemporal complexity of brain activity. The experiments show a direct relationship between this complexity and the difficulty of the task. A natural interpretation is that higher levels of mental load recruit a larger number of independent neural processes that contribute to complex brain dynamics. These results suggest the possibility that the relative change in correlation dimension can be a useful global measure of brain dynamics, e.g., in determining the levels of mental activity, even if little is known about the underlying neurological processes.

Altered states of consciousness: review of experimental data obtained with a multiple techniques approach

OBJECTIVES

To investigate the psychophysiologic mechanisms of an altered state of consciousness (ASC) produced via systematic mental training by correlating the results of multiple computerized bioelectrographic measurements.

DESIGN

All subjects were tested, using a set of modern computerized techniques comprising digital electroencephalography, measurement of the low-frequency bilateral activity of the brain, evoked bioelectrographic signals measured by computerized Kirlian photography (otherwise called gas discharge visualization [GDV]), self-reporting by subjects, linguistic testing, and profiling of mood states.

LOCATION

Sweden and Russia from 1996 to 1999.

SUBJECTS

Young volunteers (61) who underwent systematic mental training for not less than 7 weeks. Members of the control group (56) were not engaged in mental training.

RESULTS

All participants involved in the systematic mental training showed significant positive changes in their psychoemotional status after 7 weeks of mental training. All of the techniques showed specific changes that might be associated with an ASC in the subjects. The Kirlian (GDV) patterns showed a form of "explosive activation," which was stable, reproducible, and correlated with an ASC. This led the authors to introduce the concept of short-term activation of the induced bioelectrographic processes and enabled the properties of this ACS to be determined for the first time. There were practically no changes in the control group.

CONCLUSIONS

ASC activation took place with harmonization of the biopotential field of the brain, the psychic state, and the bioenergy fields. This is attributed to changes in both the psychosomatic and psychoenergetic autoregulation. This conclusion is of vital importance for understanding what happens in systematic mental training and understanding the fundamentals of bioenergetic and psychosomatic medicine.

The balance beam in the balance: reflections on rules, relational complexity, and developmental processes

The lead articles by Jansen and van der Maas (2002, this issue) and Halford, Andrews, Dalton, Boag, and Zielinski (2002, this issue) raise numerous questions concerning the development of rule use and how best to assess it. In this Reflection, we focus on the following: (a) When can one infer the use of a rule? (b) What are the mechanisms underlying the development of rule use? and (c) What is the relation between understanding and execution? In addressing these questions, we contrast relational complexity theory with cognitive complexity and control (CCC) theory.

Memory encoding and retrieval in frontotemporal dementia and Alzheimer's disease

Memory encoding and retrieval strategies were assessed in patients with behavior-executive variant frontotemporal dementia (FTD), language variant FTD, and Alzheimer's disease (AD) using verbal and visuospatial supraspan learning tests. FTD patients obtained higher free recall, cued recall, and recognition scores than AD patients. Comparison of free recall scores with cued recall and recognition scores was similar in the 3 dementia groups. Groups did not differ in semantic clustering strategies during learning, but serial-order recall was more common in FTD patients. These data do not support the idea that FTD patients' poor memory is due to a selective retrieval disorder, though FTD patients may fail to implement sophisticated organizational strategies during learning. FTD patients' retained capacity for encoding new information into long-term declarative memory is likely due to relatively spared medial temporal lobe involvement.

Development of rules and strategies: balancing the old and the new

The experiments described in the lead articles replicate findings from previous studies of development of knowledge about balance scales, add several new findings, and raise four key questions: (a) How can rule use best be assessed? (b) How can we reconcile systematic use of rules with variable use of strategies? (c) When do children begin to use rules? and (d) How do children generate new rules? In this Reflection, we summarize current understanding of development of knowledge about balance scales and consider each of the four questions.

Bridging the gap between theory and model: a reflection on the balance scale task

At first glance, the two lead articles in this issue share little except the balance scale task, yet we view them as complementary rather than unrelated or contradictory. Our Reflection focuses on the individual strengths of the two lead articles and, to a greater extent, the potential power of their combined perspectives. Our general approach is to allow psychological theory to suggest a model of performance that can both evaluate specific theoretical claims and reveal important features of the data that had been previously obscured using conventional statistical analyses. Our guiding principle is that model, theory, and data all should be connected.

Counting in sign language

Do the visuomanual modality and the structure of the sequence of numbers in sign language have an impact on the development of counting and its use by deaf children? The sequence of number signs in Belgian French Sign Language follows a base-5 rule while the number sequence in oral French follows a base-10 rule. The accuracy and use of sequence number string were investigated in hearing children varying in age from 3 years 4 months to 5 years 8 months and in deaf children varying in age from 4 years to 6 years 2 months. Three tasks were used: abstract counting, object counting, and creation of sets of a given cardinality. Deaf children exhibited age-related lags in their knowledge of the number sequence; they made different errors from those of hearing children, reflecting the rule-bound nature of sign language. Remarkably, their performance in object counting and creating sets of given cardinality was similar to that of hearing children who had a longer sequence number string, indicating a better use of counting than predicted by their knowledge of the linguistic sequence of numbers.

Young children's performance on the balance scale: the influence of relational complexity

Three experiments investigated the effect of complexity on children's understanding of a beam balance. In nonconflict problems, weights or distances varied, while the other was held constant. In conflict items, both weight and distance varied, and items were of three kinds: weight dominant, distance dominant, or balance (in which neither was dominant). In Experiment 1, 2-year-old children succeeded on nonconflict-weight and nonconflict-distance problems. This result was replicated in Experiment 2, but performance on conflict items did not exceed chance. In Experiment 3, 3- and 4-year-olds succeeded on all except conflict balance problems, while 5- and 6-year-olds succeeded on all problem types. The results were interpreted in terms of relational complexity theory. Children aged 2 to 4 years succeeded on problems that entailed binary relations, but 5- and 6-year-olds also succeeded on problems that entailed ternary relations. Ternary relations tasks from other domains--transitivity and class inclusion--accounted for 93% of the age-related variance in balance scale scores.