Correlated structure of neuronal firing in macaque visual cortex limits information for binocular depth discrimination

Variability in cortical neural activity potentially limits sensory discriminations. Theoretical work shows that information required to discriminate two similar stimuli is limited by the correlation structure of cortical variability. We investigated these information-limiting correlations by recording simultaneously from visual cortical areas V1 and V4 in macaque monkeys, performing a binocular, stereo-depth discrimination task. Within both areas, noise correlations on a rapid temporal scale (20-30ms) were stronger for neuron-pairs with similar selectivity for binocular depth, meaning that these correlations potentially limit information for making the discrimination. Between-area correlations (V1 to V4) were different, being weaker for neuron pairs with similar tuning, and having a slower temporal scale (100+ms). Fluctuations in these information-limiting correlations just prior to the detection event were associated with changes in behavioral accuracy. Although these correlations limit the recovery of information about sensory targets, their impact may be curtailed by integrative processing of signals across multiple brain areas.

Spatial Relations Trigger Visual Binding of People

To navigate the social world, humans must represent social entities and the relationships between those entities, starting with spatial relationships. Recent research suggests that two bodies are processed with particularly high efficiency in visual perception, when they are in a spatial positioning that cues interaction, that is, close and face-to-face. Socially relevant spatial relations such as facingness may facilitate visual perception by triggering grouping of bodies into a new integrated percept, which would make the stimuli more visible and easier to process. We used EEG and a frequency-tagging paradigm to measure a neural correlate of grouping (or visual binding), while female and male participants saw images of two bodies face-to-face or back-to-back. The two bodies in a dyad flickered at frequency F1 and F2, respectively, and appeared together at a third frequency Fd (dyad frequency). This stimulation should elicit a periodic neural response for each body at F1 and F2, and a third response at Fd, which would be larger for face-to-face (vs. back-to-back) bodies, if those stimuli yield additional integrative processing. Results showed that responses at F1 and F2 were higher for upright than for inverted bodies, demonstrating that our paradigm could capture neural activity associated with viewing bodies. Crucially, the response to dyads at Fd was larger for face-to-face (vs. back-to-back) dyads, suggesting integration mediated by grouping. We propose that spatial relations that recur in social interaction (i.e., facingness) promote binding of multiple bodies into a new representation. This mechanism can explain how the visual system contributes to integrating and transforming the representation of disconnected body shapes into structured representations of social events.

Integrative frontal-parietal dynamics supporting cognitive control

Coordinating among the demands of the external environment and internal plans requires cognitive control supported by a fronto-parietal control network (FPCN). Evidence suggests that multiple control systems span the FPCN whose operations are poorly understood. Previously (Nee and D'Esposito, 2016; 2017), we detailed frontal dynamics that support control processing, but left open their role in broader cortical function. Here, I show that the FPCN consists of an external/present-oriented to internal/future-oriented cortical gradient extending outwardly from sensory-motor cortices. Areas at the ends of this gradient act in a segregative manner, exciting areas at the same level, but suppressing areas at different levels. By contrast, areas in the middle of the gradient excite areas at all levels, promoting integration of control processing. Individual differences in integrative dynamics predict higher-level cognitive ability and amenability to neuromodulation. These data suggest that an intermediary zone within the FPCN underlies integrative processing that supports cognitive control.

Self-defining Memories (Their Affect, Structure, Meaning, and Content) in Relation to Temperament, Trait Domains, and Psychological Adjustment

We partly replicated and significantly extended research linking four features of self-defining memories (SDMs) – affect, structure, meaning, and content – to personality and adjustment. By linking SDM features to temperament, the five-factor model domains, and psychopathology models (and the Big Three superfactors), we tested theories about the relationships between autobiographical memory and personality. The sample of 133 participants (1330 SDMs) was well-powered for multilevel modeling. We found support for the following claims. Affect: SDM affect was linked to positive and negative emotionality indices, consistent with trait theory and the self-memory system (SMS) model of autobiographical recall. Structure: SDM specificity vs. overgenerality related to indices of constraint and internalizing tendencies, lending support to the executive dysfunction and emotional disorder theories of overgeneral memory. Tests of the avoidance hypotheses of overgeneral memory were less conclusive. Meaning: Integrative processing in SDMs reflects healthy personality functioning. It moderated the link between SDM affect and internalizing. Content: Links between SDM content (event types and contamination themes) and personality suggest that SDMs reflect personal goals (as per the SMS model) whose fulfillment (or frustration) may indicate (mal)adjustment. This research further establishes the validity and usefulness of the SDM framework in the study of autobiographical memory, personality, and psychopathology.

Spinal neuron-glia-immune interaction in cross-organ sensitization

Inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS), historically considered as regional gastrointestinal disorders with heightened colonic sensitivity, are increasingly recognized to have concurrent dysfunction of other visceral and somatic organs, such as urinary bladder hyperactivity, leg pain, and skin hypersensitivity. The interorgan sensory cross talk is, at large, termed “cross-organ sensitization.” These organs, anatomically distant from one another, physiologically interlock through projecting their sensory information into dorsal root ganglia (DRG) and then the spinal cord for integrative processing. The fundamental question of how sensitization of colonic afferent neurons conveys nociceptive information to activate primary afferents that innervate distant organs remains ambiguous. In DRG, primary afferent neurons are surrounded by satellite glial cells (SGCs) and macrophage accumulation in response to signals of injury to form a neuron-glia-macrophage triad. Astrocytes and microglia are major resident nonneuronal cells in the spinal cord to interact, physically and chemically, with sensory synapses. Cumulative evidence gathered so far indicate the indispensable roles of paracrine/autocrine interactions among neurons, glial cells, and immune cells in sensory cross-activation. Dichotomizing afferents, sensory convergency in the spinal cord, spinal nerve comingling, and extensive sprouting of central axons of primary afferents each has significant roles in the process of cross-organ sensitization; however, more results are required to explain their functional contributions. DRG that are located outside the blood-brain barrier and reside upstream in the cascade of sensory flow from one organ to the other in cross-organ sensitization could be safer therapeutic targets to produce less central adverse effects.

Spatial relations trigger visual binding of people

To navigate the social world, humans must represent social entities, and the relationships between those entities, starting with the spatial relationships. Recent research suggests that two bodies are processed with particularly high efficiency in visual perception, when they are in a spatial positioning that cues interaction, i.e. close and face-to-face. Socially relevant spatial relations such as facingness may facilitate visual perception by triggering grouping of bodies into a new integrated percept, which would make the stimuli more visible and easier to process. We used electroencephalography and a frequency-tagging paradigm to measure a neural correlate of grouping (or visual binding), while female and male participants saw images of two bodies face-to-face or back-to-back. The two bodies in a dyad flickered at the frequencies F1 and F2, respectively, and appeared together at a third frequency Fd (dyad frequency). This stimulation should elicit a periodic neural response for each single body at F1 and F2, and a third response at Fd, which would be larger for face-to-face (vs. back-to-back) bodies, if those stimuli yield additional integrative processing. Results showed that responses at F1 and F2 were higher for upright than for inverted bodies, demonstrating that our paradigm could capture body-specific activity. Crucially, the response to dyads at Fd was larger for face-to-face (vs. back-to-back) dyads, suggesting integration mediated by grouping. Thus, spatial relations that recur in social interaction (i.e., facingness) may promote binding of multiple bodies into a new representation. This mechanism can explain how the visual system contributes to integrating and transforming the representation of disconnected individual body-shapes into structured representations of social events.

Integrative Frontal-Parietal Dynamics Supporting Cognitive Control

Coordinating among the demands of the external environment and internal plans requires cognitive control supported by a fronto-parietal control network (FPCN). Evidence suggests that multiple control systems span the FPCN whose operations are poorly understood. Previously (Nee and D’Esposito, 2016; 2017), we detailed frontal dynamics that support control processing, but left open their role in broader cortical function. Here, I show that the FPCN consists of an external/present-oriented to internal/future-oriented cortical gradient extending outwardly from sensory-motor cortices. Areas at the ends of this gradient act in a segregative manner, exciting areas at the same level, but suppressing areas at different levels. By contrast, areas in the middle of the gradient excite areas at all levels, promoting integration of control processing. Individual differences in integrative dynamics predict higher-level cognitive ability and amenability to neuromodulation. These data suggest that an intermediary zone within the FPCN underlies integrative processing that supports cognitive control.Impact StatementThis study shows that intermediary areas within the FPCN are critical for integrating control processing, cognitive ability, and amenability to neuromodulation.

Correlated structure of neuronal firing in macaque visual cortex limits information for binocular depth discrimination

ABSTRACTVariability in cortical neural activity potentially limits sensory discriminations. Theoretical work shows that information required to discriminate two similar stimuli is limited by the correlation structure of cortical variability. We investigated these information-limiting correlations by recording simultaneously from visual cortical areas V1 and V4 in macaque monkeys, performing a binocular, stereo-depth discrimination task. Within both areas, noise correlations on a rapid temporal scale (20-30ms) were stronger for neuron-pairs with similar selectivity for binocular depth, meaning that these correlations potentially limit information for making the discrimination. Between-area correlations (V1 to V4) were different, being weaker for neuron pairs with similar tuning, and having a slower temporal scale (100+ms). Fluctuations in these information-limiting correlations just prior to the detection event were associated with changes in behavioural accuracy. Although these correlations limit the recovery of information about sensory targets, their impact may be curtailed by integrative processing of signals across multiple brain areas.

Disrupted brain structural connectivity in Pediatric Bipolar Disorder with psychosis

Bipolar disorder (BD) has been linked to disrupted structural and functional connectivity between prefrontal networks and limbic brain regions. Studies of patients with pediatric bipolar disorder (PBD) can help elucidate the developmental origins of altered structural connectivity underlying BD and provide novel insights into the aetiology of BD. Here we compare the network properties of whole-brain structural connectomes of euthymic PBD patients with psychosis, a variant of PBD, and matched healthy controls. Our results show widespread changes in the structural connectivity of PBD patients with psychosis in both cortical and subcortical networks, notably affecting the orbitofrontal cortex, frontal gyrus, amygdala, hippocampus and basal ganglia. Graph theoretical analysis revealed that PBD connectomes have fewer hubs, weaker rich club organization, different modular fingerprint and inter-modular communication, compared to healthy participants. The relationship between network features and neurocognitive and psychotic scores was also assessed, revealing trends of association between patients’ IQ and affective psychotic symptoms with the local efficiency of the orbitofrontal cortex. Our findings reveal that PBD with psychosis is associated with significant widespread changes in structural network topology, thus strengthening the hypothesis of a reduced capacity for integrative processing of information across brain regions. Localised network changes involve core regions for emotional processing and regulation, as well as memory and executive function, some of which show trends of association with neurocognitive faculties and symptoms. Together, our findings provide the first comprehensive characterisation of the alterations in local and global structural brain connectivity and network topology, which may contribute to the deficits in cognition and emotion processing and regulation found in PBD.