Brain Structure & Function最新文献

Genetic studies have increasingly identified key mechanisms that underlie individual and phylogenetic variation in behavioral and brain phenotypes. Here, we used quantitative genetics to estimate heritability in whole brain and region-specific variation in gray matter in a sample of captive chimpanzees. We included the contributions of sex and age to individual variation in gray matter as well as their association with cognition and motor functions and found small to moderate heritability in average gray matter volume in the majority of brain regions. By contrast, weaker estimates of heritability were found when considering asymmetries in gray matter across brain regions. Age was inversely associated with gray matter volume for the frontal lobe and the basal forebrain after accounting for sex and relatedness of the chimpanzees. Chimpanzees that had higher cognition scores were found to have greater leftward asymmetries in the regions comprising the frontal lobe and basal forebrain component. Further, chimpanzees with better performance on a tool use task had higher gray matter volumes in the frontal and basal forebrain regions. However, no genetic associations were found between tool use performance or cognition and the average frontal or basal forebrain gray matter volumes or asymmetry.

Mental imagery is widely used in cognitive neuroscience and rehabilitation studies, yet their neural mechanisms remain not fully understood. In this study, we investigated neural correlates of motor and tactile imagery using simultaneous electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) recordings. A total of 16 healthy participants performed motor and tactile imagery tasks while brain activity was assessed. We analyzed event-related desynchronization (ERD) of the mu-rhythm and hemodynamic responses in sensory-motor regions. Similar spatio-temporal EEG patterns were observed for both motor and tactile imagery conditions (e.g., prominent contralateral ERD at C3). Hemodynamic responses differed: motor imagery elicited activation in both precentral and postcentral regions (p = 0.433), whereas tactile imagery predominantly engaged postcentral regions. The latter effect reached significance only in the functional channels of interest (fCOI) analysis (p = 0.003) and showed a non-significant trend across the full anatomical channel groups (p = 0.101). Correlation analysis revealed a strong across-subject correlation (r = 0.84; p < 0.001) between ERD values in motor and tactile imagery, but no correlation between ERD and hemodynamic responses. Linear mixed model analysis revealed significant (p < 0.001) associations between precentral and postcentral HRs for both MI and TI. These findings suggest that although motor and tactile imagery share common sensorimotor engagement at the electrophysiological level, their hemodynamic signatures are distinct. The absence of linear associations between modalities highlights the complexity of brain dynamics and the importance of multimodal assessments. The findings have implications for the design of brain-computer interfaces and rehabilitation protocols using mental imagery.

In the macaque brain most cortical areas are connected through the corpus callosum to the same or different areas of the contralateral hemisphere (homotopic and heterotopic callosal connections). Many studies have described the callosal connectivity of several cortical areas, but the proportion of callosal vs. ipsilateral afferences and, except for frontal motor areas, of homotopic vs. heterotopic afferences is still unknown. We have analyzed qualitatively and quantitatively the distribution of callosal projecting neurons (CPNs) after neural tracer injections in prefrontal, frontal motor and opercular, and parietal areas (36 tracer injections in 20 macaques). The percentage of CPNs with respect to the total number of labeled neurons (ipsi + contra), with few exceptions, was at least 5% and though quite variable tended to be higher for prefrontal (~ 17%) and premotor (~ 14%), and lower for parietal (~ 9%) areas. For most areas, heterotopic afferences were richer than homotopic ones and for some (e.g., F6 and F3) the areal distribution of CPNs was almost similar to that of the ipsilateral labeling. Furthermore, in areas 24, F6, and F3 the amount of CPNs tended to be relatively high. Finally, the laminar distribution of CPNs could differ from that of the ipsilateral labeling and varied according to the projecting and/or the target area. The present data provide a general framework, though still not complete, of the interhemispheric connectivity in the primate brain and could be useful for a better understanding of the interhemispheric interactions in bimanual coordination, sensorimotor integration, and cognitive functions.

The inferior olive (IO) is an important region for motor learning and movement coordination. IO activity carried by the climbing fiber (CF) projection to the Purkinje neurons in the cerebellar cortex drives the complex spike activity, central to theories of cerebellar function. Unlike many other neurons in the olivo-cerebeller system, IO neurons are not spontaneously active but rather spike in response to inputs from various regions of the brain. The superior colliculus (SC), a midbrain structure known for its role in orienting behaviors, is one of the input sources to the IO. Here, we investigate the SC projections to the IO using viral tracers, calcium imaging, and optogenetic stimulation. We reveal that, in addition to the known projections to the medial accessory olive (MAO), the SC axons also project to the ventral principal olive (PO). We show that SC axons terminate on both dendritic shafts and spines of IO neurons, potentially influencing not only spiking probability, but also the network synchronization mediated by gap junction coupling on dendritic spines. As a demonstration of the SC axons' ability to drive IO spiking, we employ in vivo calcium imaging of the IO and show that optogenetic activation of SC inputs can drive spiking and modulate overall synchronization of the IO. This study provides a fundamental basis for studying the behavioral significance of the SC-IO pathway in mice.

An organism's sense of direction depends on vestibular input to thalamic and forebrain structures. The supragenual nucleus (SGN) sits at a prime location in the network to convey vestibular signals forward to update the representation of head direction (HD) with ongoing head movement. The SGN receives anatomical projections from the medial vestibular nuclei and nucleus prepositus hypoglossi and prior reports have suggested that the SGN sends projections to both the dorsal tegmental nucleus (DTN) and lateral mammillary nucleus (LMN), two midbrain nuclei crucial in generating a representation of current HD. It is unknown, however, whether distinct or overlapping populations in SGN project to these structures, which has implications for how the SGN plays a role in generating and updating the HD signal. We performed a dual-color retrograde tracer study to determine whether the DTN and LMN projections from SGN arise from the same or different populations of cells. We report that the SGN→DTN projection is markedly stronger than that to LMN, filling most cells within the SGN, while SGN cells projecting to LMN tended to be smaller and sparser. We also found a small population of SGN cells projecting to both DTN and LMN. Further, our results indicate the presence of a large population of neurons in SGN that project only to the contralateral DTN and that these cells have little overlap with the ipsilateral projection to LMN. These results have implications for how the HD signal is generated within the DTN-LMN network.

The medial prefrontal cortex (mPFC) serves as a critical hub in addiction pathology across binge/intoxication, withdrawal/negative affect, and preoccupation/anticipation/craving stages. This review provides the roles of the mPFC in different stages of addiction, and a focus on the mPFC neurotransmitter systems, neural circuits, molecules and synaptic adaptations on the regulation of addictive behaviors. Neurotransmitter systems of dopaminergic, glutamatergic, and GABAergic imbalances are related to pathological addiction. Circuits of dynamic dysregulation in the mPFC interaction with the striatum, nucleus accumbens (NAc), ventral tegmental area (VTA), dorsal raphe nucleus (DRN), and amygdala drive stage-specific behaviors, such as the prelimbic cortex (PL)→NAc core promoting cocaine-seeking, the infralimbic cortex (IL)→NAc shell suppressing relapse. Alterations in excitation-inhibition of microcircuits pyramidal neurons, GABAergic interneurons impair top-down regulation. Synaptic plasticity induced by drugs is involved in pathological stage-specific addiction, such as persistent craving and compulsive behaviors. Targeting the mPFC circuits offers promising therapeutic strategies for addiction intervention.