Who is that? Brain networks and mechanisms for identifying individuals

Social animals can identify conspecifics by many forms of sensory input. However, whether the neuronal computations that support this ability to identify individuals rely on modality-independent convergence or involve ongoing synergistic interactions along the multiple sensory streams remains controversial. Direct neuronal measurements at relevant brain sites could address such questions, but this requires better bridging the work in humans and animal models. Here, we overview recent studies in nonhuman primates on voice and face identity-sensitive pathways and evaluate the correspondences to relevant findings in humans. This synthesis provides insights into converging sensory streams in the primate anterior temporal lobe (ATL) for identity processing. Furthermore, we advance a model and suggest how alternative neuronal mechanisms could be tested

Bipolar disorder and neurophysiologic mechanisms

Recent studies have suggested that some variants of bipolar disorder (BD) may be due to hyperconnectivity between orbitofrontal (OFC) and temporal pole (TP) structures in the dominant hemisphere. Some initial MRI studies noticed that there were corpus callosum abnormalities within specific regional areas and it was hypothesized that developmentally this could result in functional or effective connectivity changes within the orbitofrontal-basal ganglia-thalamocortical circuits. Recent diffusion tensor imaging (DTI) white matter fiber tractography studies may well be superior to region of interest (ROI) DTI in understanding BD. A “ventral semantic stream” has been discovered connecting the TP and OFC through the uncinate and inferior longitudinal fasciculi and the elusive TP is known to be involved in theory of mind and complex narrative understanding tasks. The OFC is involved in abstract valuation in goal and sub-goal structures and the TP may be critical in binding semantic memory with person–emotion linkages associated with narrative. BD patients have relative attenuation of performance on visuoconstructional praxis consistent with an atypical localization of cognitive functions. Multiple lines of evidence suggest that some BD alleles are being selected for which could explain the enhanced creativity in higher-ability probands. Associations between ROI’s that are not normally connected could explain the higher incidence of artistic aptitude, writing ability, and scientific achievements among some mood disorder subjects

Age-Related Changes in Perirhinal Cortex Sensitivity to Configuration and Part Familiarity and Connectivity to Visual Cortex

The perirhinal cortex (PRC) is a medial temporal lobe (MTL) structure known to be involved in assessing whether an object is familiar (i.e., meaningful) or novel. Recent evidence shows that the PRC is sensitive to the familiarity of both whole object configurations and their parts, and suggests the PRC may modulate part familiarity responses in V2. Here, using functional magnetic resonance imaging (fMRI), we investigated age-related decline in the PRC’s sensitivity to part/configuration familiarity and assessed its functional connectivity to visual cortex in young and older adults. Participants categorized peripherally presented silhouettes as familiar (“real-world”) or novel. Part/configuration familiarity was manipulated via three silhouette configurations: Familiar (parts/configurations familiar), Control Novel (parts/configurations novel), and Part-Rearranged Novel (parts familiar, configurations novel). “Real-world” judgments were less accurate than “novel” judgments, although accuracy did not differ between age groups. The fMRI data revealed differential neural activity, however: In young adults, a linear pattern of activation was observed in left hemisphere (LH) PRC, with Familiar > Control Novel > Part-Rearranged Novel. Older adults did not show this pattern, indicating age-related decline in the PRC’s sensitivity to part/configuration familiarity. A functional connectivity analysis revealed a significant coupling between the PRC and V2 in the LH in young adults only. Older adults showed a linear pattern of activation in the temporopolar cortex (TPC), but no evidence of TPC-V2 connectivity. This is the first study to demonstrate age-related decline in the PRC’s representations of part/configuration familiarity and its covariance with visual cortex

Cholinergic system changes of falls and freezing of gait in Parkinson’s disease

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149240/1/ana25430_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149240/2/ana25430.pd

Hippocampus size predicts fluid intelligence in musically trained people

Introduction Neurogenesis persists in the human adult hippocampus1 and the survival of new progenitor cells is enhanced by learning activities2. Using the musician's brain as a model for cortical plasticity, musical training induced functional adaptations of the hippocampus have been demonstrated3,4. Furthermore, there is evidence for a positive correlation between hippocampus size and fluid intelligence5, encompassing aspects of attention, working memory and executive functions6. Previous data strongly suggest that musical training impacts on such higher order cognitive functions7,14. Following these findings we hypothesize a linkage between hippocampus size and fluid intelligence in musically trained people. Methods Participants: Three groups - piano experts (E, n=20), piano amateurs (A, n=20) and nonmusicians (N, n=19), matched by age and gender. Task: short version of the Raven's Test, Advanced Progressive Matrices (time limit 15 minutes). Structural MRI: manual segmentation8,9,10,11,12 of left (LH) and right (RH) hippocampi done by a single investigator blinded for group belonging and ID of each subject, software MRIcroN13 (Fig. 1) Statistics: one-way ANOVAs on Raven performance and hippocampus volume; Fisher's r to z transformations; robust multiple regression models for each hemisphere: (i) to predict Raven performance by hippocampus volume and (ii) to test whether this prediction is modulated by the factor of musical training. Robust regression analysis (implemented by statistical software R) represents a valid alternative to least square regression analysis when data is potentially contaminated by single influential observations. Results One way ANOVAs with three levels of expertise: no main effects of Expertise neither in Raven's Test performance nor in hippocampus volumes. No main effect of Lateralization (Fig. 2). Pooling of musicians (M=A+E) justified as no difference in predictive power exists between A and E, neither in the left nor in the right hemisphere. LH: z=0.84, p=0.401, RH: z=-0.45, p=0.623. Robust multiple regression analysis testing the prediction of Raven's performance by hippocampus size, modulated by musicianship (two levels: N, M(A+E)): - Left hemisphere: Significant interaction (t=2.221, p=.030), revealing that prediction of Raven's performance by hippocampus size is modulated by musical training: N (beta =.03) and M (beta =.46). - Right hemisphere: Significant interaction (t=2.003, p=.050), revealing that prediction of Raven's performance by hippocampus size is modulated by musical training: N (beta =.01) and M (beta =.38). Conclusion Hippocampus size significantly predicts fluid intelligence performance in musically experienced subjects but not in musically naïve ones. This result represents a striking additional corroboration of musicians' brain plasticity. It seems highly plausible that a longlasting complex activity like musical instrumental training from childhood into adulthood induced an increase in hippocampus size associated with enhanced logical reasoning. Further research is needed to investigate cognitive functions favored by musical training and possible consequent impact on the development of peculiar brain structures. NB: This research was performed within the framework of an ongoing research project performed by Clara James (principal investigator) and postdoc collaborator Mathias Oechslin entitled "Behavioral, neuro-functional and neuro-anatomical correlates of experience dependant music perception" (FNS 100014_125050). This research project investigates brain adaptations in correlation with changes of behavior in young adults with varying musical experience, anticipating gradual changes in behavior, brain functioning and brain structure with degree of musical aptitude. In this frame, I did the data collection of hippocampus volumes and analyzed the results in correlation with a literature research on the subject

Integrating visual and tactile information in the perirhinal cortex

By virtue of its widespread afferent projections, perirhinal cortex is thought to bind polymodal information into abstract object-level representations. Consistent with this proposal, deficits in cross-modal integration have been reported after perirhinal lesions in nonhuman primates. It is therefore surprising that imaging studies of humans have not observed perirhinal activation during visual–tactile object matching. Critically, however, these studies did not differentiate between congruent and incongruent trials. This is important because successful integration can only occur when polymodal information indicates a single object (congruent) rather than different objects (incongruent). We scanned neurologically intact individuals using functional magnetic resonance imaging (fMRI) while they matched shapes. We found higher perirhinal activation bilaterally for cross-modal (visual–tactile) than unimodal (visual–visual or tactile–tactile) matching, but only when visual and tactile attributes were congruent. Our results demonstrate that the human perirhinal cortex is involved in cross-modal, visual–tactile, integration and, thus, indicate a functional homology between human and monkey perirhinal cortices

Where do bright ideas occur in our brain? Meta-analytic evidence from neuroimaging studies of domain-specific creativity

Many studies have assessed the neural underpinnings of creativity, failing to find a clear anatomical localization. We aimed to provide evidence for a multi-componential neural system for creativity. We applied a general activation likelihood estimation (ALE) meta-analysis to 45 fMRI studies. Three individual ALE analyses were performed to assess creativity in different cognitive domains (Musical, Verbal, and Visuo-spatial). The general ALE revealed that creativity relies on clusters of activations in the bilateral occipital, parietal, frontal, and temporal lobes. The individual ALE revealed different maximal activation in different domains. Musical creativity yields activations in the bilateral medial frontal gyrus, in the left cingulate gyrus, middle frontal gyrus, and inferior parietal lobule and in the right postcentral and fusiform gyri. Verbal creativity yields activations mainly located in the left hemisphere, in the prefrontal cortex, middle and superior temporal gyri, inferior parietal lobule, postcentral and supramarginal gyri, middle occipital gyrus, and insula. The right inferior frontal gyrus and the lingual gyrus were also activated. Visuo-spatial creativity activates the right middle and inferior frontal gyri, the bilateral thalamus and the left precentral gyrus. This evidence suggests that creativity relies on multi-componential neural networks and that different creativity domains depend on different brain regions

Anterior insula degeneration in frontotemporal dementia

The human anterior insula is anatomically and functionally heterogeneous, containing key nodes within distributed speech–language and viscero-autonomic/social–emotional networks. The frontotemporal dementias selectively target these large-scale systems, leading to at least three distinct clinical syndromes. Examining these disorders, researchers have begun to dissect functions which rely on specific insular nodes and networks. In the behavioral variant of frontotemporal dementia, early-stage frontoinsular degeneration begets progressive “Salience Network” breakdown that leaves patients unable to model the emotional impact of their own actions or inactions. Ongoing studies seek to clarify local microcircuit- and cellular-level factors that confer selective frontoinsular vulnerability. The search for frontotemporal dementia treatments will depend on a rich understanding of insular biology and could help clarify specialized human language, social, and emotional functions

The Active Bayesian Brain and the Rorschach Task

The Rorschach offers a unique and interesting paradigm from the perspective of the (Bayesian) brain. This contribution to the cross-disciplinary special issue considers the Rorschach from the perspective of perceptual inference in the brain and how it might inform subject-specific differences in perceptual synthesis. Before doing so, we provide a broad overview of active inference in its various manifestations. In brief, active inference supposes that our perceptions are the best hypothesis to explain sensory impressions. On a Bayesian account, the requisite belief updating rests sensitively upon the precision or confidence ascribed to sensory input, relative to prior beliefs about the causes of sensations. This focus - on the balance between sensory and prior precision - has been a useful construct in both cognitive science (e.g., as a formal explanation for attention) and neuropsychology (e.g., as a formal explanation for aberrant or false inference in hallucinations). In this setting, false inference is generally understood as abnormally high precision afforded to high-level hypotheses or explanations for visual input, which may compensate for a failure to attenuate sensory precision. On this view, the Rorschach offers an interesting paradigm because the amount of precise information about the causes of visual input is deliberately minimized - and rendered ambiguous - thereby placing greater emphasis on prior beliefs entertained by the respondent. We close by exploring this issue and several other areas of intersection between Rorschach responding and active inference

Perirhinal cortex contributes to accuracy in recognition memory and perceptual discriminations.

The prevailing view of the medial temporal lobe (MTL) holds that its structures are dedicated to long-term declarative memory. Recent evidence challenges this position, suggesting that perirhinal cortex (PRc) in the MTL may also play a role in perceptual discriminations of stimuli with substantial visual feature overlap. Relevant neuropsychological findings in humans have been inconclusive, likely because studies have relied on patients with large and variable MTL lesions. Here, we conducted a functional magnetic resonance imaging study in healthy individuals to determine whether PRc shows a performance-related involvement in perceptual oddball judgments that is comparable to its established role in recognition memory. Morphed faces were selected as stimuli because of their large degree of feature overlap. All trials involved presentation of displays with three faces. The perceptual oddball task required identification of the face least similar to the other display members. The memory task involved forced-choice recognition of a previously studied face. When levels of behavioral performance were matched, we observed comparable levels of activation in right PRc for both tasks. Moreover, right PRc activity differentiated between accurate and inaccurate trials in both tasks. Together these results indicate that declarative memory demands are not a prerequisite for a performance-related engagement of PRc and that the introduction of such declarative memory demands in an otherwise closely matched perceptual task does not necessarily lead to an increase in PRc involvement. As such our findings show that declarative memory and perception are not as clearly separable at the level of MTL functioning as traditionally thought