The common magnitude code underlying numerical and size processing for action but not for perception

The interaction between numbers and action-related process has received increasing attention in the literature of numerical cognition. In the current study, two dual-task experiments were conducted to explore the interaction among numerical, prehension, and perceptual color/size judgments. The results revealed the commonality and distinctness of the magnitude representations that are involved in these tasks. Specifically, a photograph of a graspable object with a superimposed Arabic digit was presented in each trial. Participants were required to first judge the parity of the digit with a manual response while simultaneously planning a subsequent vocal response pertaining to the depicted object. When parity and action judgments were performed close in time, the compatibility effect between the numerical magnitude of the digit and the appropriate action (pinch vs. clutch) for the object was demonstrated in both manual and vocal responses. In contrast, such compatibility effect was absent when parity judgment was coupled with color-related or perceptual size judgment. The findings of the current study support the existence of a common magnitude code underlying numerical and non-numerical dimensions for action-related purposes, as proposed by the ATOM model (Walsh in Trends Cogn Sci 7:483–488, 2003). Furthermore, based on the selective presence of the compatibility effect, we argue that the interaction among different quantity dimensions conforms to the “dorsal-action and ventral-perception” organizational principle of the human brain.

Notation-dependent processing of numerical magnitude: Electrophysiological evidence from Chinese numerals

To investigate whether the semantic processing of numbers is notation-dependent or notation-independent, three notation stimuli—Arabic digits, Chinese numerals written in simple form (Ch-S), and Chinese numerals written in complex form (Ch-C)—were presented to participants. The participants were asked to judge which target numeral (numerical values 1-4 and 6-9) was “smaller or larger than 5” while event-related potentials (ERPs) were recorded. Electrophysiological results revealed that the voltage activity associated with numerical semantic processing was largest across temporo-occipital-parietal electrode sites, regardless of input formats. However, the time windows for the semantic processing of numerals did not overlap across notations. Furthermore, the main effects of notation and notation/distance interaction were still observed at the stage of numerical magnitude processing, suggesting that notation might affect the semantic processing of numbers. In addition, a right-lateralized N1 for both Arabic digits and Ch-C numbers, and a bilateral N1 for Ch-S numbers, were observed; these data imply that number processing in Chinese speakers may be different from that in Western speakers.     

Distributed cognition: an alternative model of cognition for medical informatics

BACKGROUND: Medical informatics has been guided by an individual-centered model of human cognition, inherited from classical theory of mind, in which knowledge, problem-solving, and information-processing responsible for intelligent behavior all derive from the inner workings of an individual agent. OBJECTIVES AND RESULTS: In this paper we argue that medical informatics commitment to the classical model of cognition conflates the processing performed by the minds of individual agents with the processing performed by the larger distributed activity systems within which individuals operate. We review trends in cognitive science that seek to close the gap between general-purpose models of cognition and applied considerations of real-world human performance. One outcome is the theory of distributed cognition, in which the unit of analysis for understanding performance is the activity system which comprises a group of human actors, their tools and environment, and is organized by a particular history of goal-directed action and interaction. CONCLUSION: We describe and argue for the relevance of distributed cognition to medical informatics, both for the study of human performance in healthcare and for the design of technologies meant to enhance this performance.     

Depressive cognition: Self-reference and depth of processing

Cognitive models of depression, which propose that depression is associated with negatively biased thinking, have typically focused on either the content or the processes of depressive cognition. Content-based models suggest that depressive thought is more negative for self-relevant than for externally-focused content. Process-based models propose that early, automatic processes are not negatively biased in depression, but that deeper processes are biased. The current review evaluates evidence for both the self-relevant content and depth of processing accounts, and concludes that there is substantial evidence for both models. I call for further research which integrates content and process-based approaches by using self-relevant stimuli and cognitive measures which precisely identify the specific attention, memory, and interpretation processes affected in depression.     

Functional brain connectivity and cognition: effects of adult age and task demands

Previous neuroimaging research has documented that patterns of intrinsic (resting state) functional connectivity (FC) among brain regions covary with individual measures of cognitive performance. Here, we examined the relation between intrinsic FC and a reaction time (RT) measure of performance, as a function of age group and task demands. We obtained filtered, event-related functional magnetic resonance imaging data, and RT measures of visual search performance, from 21 younger adults (19–29 years old) and 21 healthy, older adults (60–87 years old). Age-related decline occurred in the connectivity strength in multiple brain regions, consistent with previous findings. Among 8 pairs of regions, across somatomotor, orbitofrontal, and subcortical networks, increasing FC was associated with faster responding (lower RT). Relative to younger adults, older adults exhibited a lower strength of this RT-connectivity relation and greater disruption of this relation by a salient but irrelevant display item (color singleton distractor). Age-related differences in the covariation of intrinsic FC and cognitive performance vary as a function of task demands.     

Combining structural and functional neuroimaging data for studying brain connectivity: a review

Different brain areas are thought to be integrated into large-scale networks to support cognitive function. Recent approaches for investigating structural organization and functional coordination within these networks involve measures of connectivity among brain areas. We review studies combining in vivo structural and functional brain connectivity data, where (a) structural connectivity analysis, mostly based on diffusion tensor imaging is paired with voxel-wise analysis of functional neuroimaging data or (b) the measurement of functional connectivity based on covariance analysis is guided/aided by structural connectivity data. These studies provide insights into the relationships between brain structure and function. Promising trends involve (a) studies where both functional and anatomical connectivity data are collected using high-resolution neuroimaging methods and (b) the development of advanced quantitative models of integration.     

Greater than the sum of its parts: a review of studies combining structural connectivity and resting-state functional connectivity

It is commonly assumed that functional brain connectivity reflects structural brain connectivity. The exact relationship between structure and function, however, might not be straightforward. In this review we aim to examine how our understanding of the relationship between structure and function in the ‘resting’ brain has advanced over the last several years. We discuss eight articles that directly compare resting-state functional connectivity with structural connectivity and three clinical case studies of patients with limited white matter connections between the cerebral hemispheres. All studies examined show largely convergent results: the strength of resting-state functional connectivity is positively correlated with structural connectivity strength. However, functional connectivity is also observed between regions where there is little or no structural connectivity, which most likely indicates functional correlations mediated by indirect structural connections (i.e. via a third region). As the methodologies for measuring structural and functional connectivity continue to improve and their complementary strengths are applied in parallel, we can expect important advances in our diagnostic and prognostic capacities in diseases like Alzheimer’s, multiple sclerosis, and stroke.     

Electrophysiological assessments of cognition and sensory processing in TBI: Applications for diagnosis, prognosis and rehabilitation

Traumatic brain injuries are often associated with damage to sensory and cognitive processing pathways. Because evoked potentials (EPs) and event-related potentials (ERPs) are generated by neuronal activity, they are useful for assessing the integrity of neural processing capabilities in patients with traumatic brain injury (TBI). This review of somatosensory, auditory and visual ERPs in assessments of TBI patients is provided with the hope that it will be of interest to clinicians and researchers who conduct or interpret electrophysiological evaluations of this population. Because this article reviews ERP studies conducted in three different sensory modalities, involving patients with a wide range of TBI severity ratings and circumstances, it is difficult to provide a coherent summary of findings. However, some general trends emerge that give rise to the following observations and recommendations: 1) bilateral absence of somatosensory evoked potentials (SEPs) is often associated with poor clinical prognosis and outcome; 2) the presence of normal ERPs does not guarantee favorable outcome; 3) ERPs evoked by a variety of sensory stimuli should be used to evaluate TBI patients, especially those with severe injuries; 4) time since onset of injury should be taken into account when conducting ERP evaluations of TBI patients or interpreting results; 5) because sensory deficits (e.g., vision impairment or hearing loss) affect ERP results, tests of peripheral sensory integrity should be conducted in conjunction with ERP recordings; and 6) patients' state of consciousness, physical and cognitive abilities to respond and follow directions should be considered when conducting or interpreting ERP evaluations.     

Impairments in cognition and resting-state connectivity of the hippocampus in elderly subjects with type 2 diabetes

Type 2 diabetes mellitus (T2DM) is associated with an increased risk of Alzheimer's disease, which involves hippocampus-mediated cognitive impairment. The present study investigated whether the resting-state functional connectivity of the hippocampus would be changed in patients with T2DM. A region of interest-based resting-state functional magnetic resonance imaging (fMRI) approach was applied to explore functional connectivity differences between 21 elderly patients with T2DM and 19 well-matched healthy controls, with all participants assessed by multi-dimensional neuropsychological tests. We found that T2DM patients performed significantly worse in the Auditory Verbal Learning Test (AVLT) (especially for Delayed Recall and Recognition) and Clock Drawing Test (CDT) when compared with the control group, and cognitive function was negatively related to BMI and HbA_1c. Importantly, the hippocampus showed reduced functional connectivity bilaterally to widespread regions, including fusiform gyrus, frontal gyrus, temporal gyrus, anterior cingulate gyrus, medial frontal gyrus, posterior cingulate gyrus, precuneus and inferior parietal lobule in T2DM patients compared to healthy controls. T2DM is associated with an impaired pattern of default network function, and the specific disconnection pattern identified may be involved in the neuropathophysiology of this disease.     

Using eye tracking to study numerical cognition: the case of the ratio effect

In both behavioural and brain-imaging studies, numerical magnitude comparison tasks have been used to glean insights into the processing and representation of numerical magnitude. The present study examined the extent to which eye movement data can be used to investigate the neurocognitive processes underlying numerical magnitude processing. Twenty-two participants performed a numerical comparison task (deciding which of two Arabic numerals represents the larger numerical magnitude) while eye tracking data was recorded. The ratio between numbers (smaller/larger) was manipulated and ranged from 0.11 to 0.89. Consistent with previous reaction time and accuracy studies, the present results demonstrated significant main effects of ratio on the number of fixations, as well as a significant main effect of correct (numerically larger) versus incorrect (numerically smaller) number on the duration of fixations. Furthermore, data from the present investigation also revealed that participants made significantly more saccades between the two numbers for large relative to small ratio trials. Moreover, the ratio effects on eye movements were uncorrelated with the effect of numerical ratio on reaction times, suggesting that eye tracking measures of number comparison may tap into a different level of numerical magnitude processing than reaction time measures do.     

Hemispheric asymmetry and emotion: lateralized parietal processing of affect and cognition

The differential cerebral processing of affect and cognition may have important implications for a more general understanding of how these two complex sets of functions differ and how they interact. Building upon recent studies of hemispheric asymmetry in emotion, the present study focused on the differential parietal processing of emotional stimuli under affective and cognitive conditions. Subjects were exposed to neutral and emotional stimuli presented under cognitive and affective instructional sets. Bilateral electroencephalographic (EEG) data showed that the principal differentiation between affective and cognitive conditions occurred in the right hemisphere, whereas the highest overall level of activation during emotional stimulation was in the left hemisphere. It was also found that affective conditions produced higher of levels of both EEG and electrodermal activity than either cognitive or neutral conditions. Finally, significant patterns of gender differentiation suggested greater focal organization for affective arousal in females than males.     

Neocentromeres and alpha satellite: a proposed structural code for functional human centromere DNA

A comparative analysis of the conserved region of primate alpha satellite DNA and of a human neocentromere is reported. The two types of centromere DNA share structural features, possibly defining mitotically functional human centromere DNA. These features consist of double dyad symmetries of a particular size, as well as short conserved base motifs adjacent to the dyad symmetries. The possible importance of these features is supported by their presence also in the centromeres of yeast. The overall resemblance between primate alpha satellite DNA and yeast centromere DNA is further strengthened by the presence of a second shared structure. This structure consists of a single dyad symmetry incorporating a particular short base sequence. In the mitotically stable human neocentromere, this second symmetry is not found in connection with the double symmetry. However, the yeast homologue of the second symmetry is responsible for stability in meiosis I, rather than for mitotic stability. If the human homolog serves a similar function, it would be expendable, except for reproduction.     

Parietal processing of affect and cognition: cerebral organization in strongly lateralized left-handed subjects

Cerebral organization for the processing of emotion and for the differential processing of affect and cognition have thus far been studied exclusively in right-handed subjects. Since handedness is related to cerebral dominance, our understanding of the neural processing of affect and cognition should be further enhanced by the study of sinistral subjects. The present study examined the differential parietal processing of emotional stimuli under affective and cognitive conditions in left-handed subjects. The subjects were exposed to emotional stimuli presented under affective and cognitive instructional sets and to neutral, control stimuli. Bilateral electroencephalographic and bilateral electrodermal activity data showed greater responsiveness to emotional than neutral stimuli but no differential lateralization of affect and cognition in left-handed subjects. Results also showed that female subjects were more responsive to emotional stimuli than male subjects. Results were interpreted as suggesting that left-handed individuals may be less strongly lateralized for the differential processing of affect and cognition than right-handed individuals and that females may have greater focal organization for the processing of emotion than males.     

A differential role for human hippocampus in novelty and contextual processing: Implications for P300

The role of the hippocampus in P300 has long been debated. Here, we present a theoretical framework that elucidates hippocampal contributions to scalp P300 based on intracranial and lesion research combined with emerging evidence on the role of the hippocampus in rapid statistical learning, memory, and novelty processing. The P300 has been divided in two subcomponents: a fronto-central P3a related to novelty and distractor processing, and a parietal P3b related to target detection. Interest in a role for hippocampus in scalp P300 was sparked by P3-like ERPs measured intracranially in human hippocampus. Subsequent medial temporal lobe lesion studies show intact scalp P3b, indicating that the hippocampus is not critical for P3b. This contrasts with the scalp P3a, which was significantly diminished in human patients with lesions in the posterior hippocampus. This suggests a differential role for hippocampus in P3a and P3b. Our framework purports that the hippocampus plays a central role in distractor processing that leads to P3a generation in cortical regions. We also propose that the hippocampus is involved at the end of the cognitive episode for both P3a and P3b implementing contextual updating. P3-like ERPs measured in hippocampus may reflect input signals from cortical regions implementing updates based on the outcome of cognitive processes underlying scalp P3, enabling a model update of the environment facilitated by the hippocampus. Overall, this framework proposes an active role for the hippocampus in novelty processing leading up to P3a generation, followed by contextual updating of the outcome of both scalp P3a and P3b.     

Initiation and spread of epileptiform discharges in the methylazoxymethanol acetate rat model of cortical dysplasia: functional and structural connectivity between CA1 heterotopia and hippocampus/neocortex

Neuronal migration disorders (NMDs) are often associated with medically intractable epilepsy. In utero injection of methylazoxymethanol acetate into pregnant rats gives rise to dysplastic cell clusters ("heterotopia") in hippocampus (and nearby regions), providing an animal model of NMD. In the present study, we have examined the structural and functional integration of hippocampal heterotopic cells into circuits that link the heterotopia with surrounding "normal" brain. Bi-directional morphological connectivity between the heterotopia and hippocampus/neocortex was demonstrated using the neurotracer, biotinylated dextran amine. Single cell recordings in hippocampal slices showed that heterotopia neurons form functional connections with the surrounding hippocampus and neocortex. However, simultaneous field recordings from the CA1 heterotopia, normotopic hippocampus, and neocortex indicated that epileptiform discharges (spontaneous events seen in slices bathed with high [K+]o and bicuculline) were rarely initiated in the heterotopia (although the heterotopia was capable of generating epileptiform discharges independently of normal brain regions). Further, in most of the experiments, the aberrant connectivity provided by CA1 heterotopia failed to function as a "bridge" for epileptiform discharges to propagate directly from low-threshold hippocampus to neocortex. These data do not support the hypothesis that NMDs (heterotopic cell populations) serve as a focus and/or trigger for epileptiform activity, and/or facilitate propagation of epileptiform events.