Neurons in some sensory areas reflect the content of working memory (WM) in their spiking activity. However, this spiking activity is seldom related to behavioral performance. We studied the responses of inferotemporal (IT) neurons, which exhibit object-selective activity, along with Frontal Eye Field (FEF) neurons, which exhibit spatially selective activity, during the delay period of an object WM task. Unlike the spiking activity and local field potentials (LFPs) within these areas, which were poor predictors of behavioral performance, the phase-locking of IT spikes and LFPs with the beta band of FEF LFPs robustly predicted successful WM maintenance. In addition, IT neurons exhibited greater object-selective persistent activity when their spikes were locked to the phase of FEF LFPs. These results reveal that the coordination between prefrontal and temporal cortex predicts the successful maintenance of visual information during WM.

As individuals age, cognitive abilities such as working memory (WM), decline. In the current study, we investigated the effect of age on WM, and elucidated sources of errors. A total of 102 healthy individuals, aged 18 to 71, participated in this research. We designed and administered a face-based visual WM task, collecting responses via a graded scale in a delayed match-to-sample reproduction task. The error of participants increased significantly as they aged. Our analysis revealed a significant age-related rise in the standard deviation of error distribution. However, there was no significant change in uniform probability with age. We found that WM performance declines through the lifespan. Investigating the sources of error, we found that the precision of WM decreased monotonously with age. The results also indicated that the probability of guessing the response as a measure of random response is not affected by age.

Primates are known for their exceptional ability to recognize faces. However, we still have much to learn about how their brains process faces when they are partially hidden. When we cover parts of a face, it affects how our brains respond, even though we still perceive the face as a whole. This suggests that complex brain networks are at work in understanding partially hidden faces. To explore this further, we studied two brain regions, the ventrolateral prefrontal cortex (vlPFC) and the inferior temporal cortex (ITC), while showing primate images of faces with parts occluded. We found that vlPFC neurons were more active when faces were partially covered, while ITC neurons preferred fully visible faces. Interestingly, the ITC seemed to process occluded faces in a separate phase after the vlPFC responded. Our research revealed a coordinated effort between these brain regions based on the level of facial obstruction. Specifically, the vlPFC seemed to play a crucial role, driving the representation of occluded faces in the later phase of ITC processing. Importantly, we also found that the brain processes occluded faces differently from those that are fully visible, suggesting specialized mechanisms for handling these situations. These findings highlight the importance of feedback from the vlPFC in understanding occluded faces in the ITC region of the brain. Understanding these neural processes not only enhances our understanding of how primates perceive faces but also provides insights into broader aspects of visual cognition.

Ablation surgeries are utilized to treat certain brain disorders. Recently, these surgeries have become more prevalent using techniques such as magnetic resonance guided focused ultrasound (MRgFUS) ablation and Gamma knife thalamotomy (GKT). However, as the thalamus plays a critical role in cognitive functions, the potential impact of these surgeries on functional connectivity and cognition is a matter of concern. Various approaches have been developed to locate the target for ablation and also investigate changes in functional connectivity before and after surgery. Functional magnetic resonance imaging (fMRI) and electroencephalogram (EEG) are widely used methods for assessing changes in functional connectivity and activity in clinical research. In this Review, we summarize the use of fMRI and EEG in thalamotomy surgeries. Our analysis shows that thalamotomy surgery can result in changes in functional connectivity in motor-related, visuomotor, and default-mode networks, as detected by fMRI. EEG data also indicate a reduction in over-activities observed in the preoperative state.

Objects are recognized in three hierarchical levels: superordinate, mid-level, and subordinate. Psychophysics shows that mid-level categories and low spatial frequency (LSF) information are rapidly recognized. However, the interaction between spatial frequency (SF) and abstraction is not well understood. To address this, we examine neural responses in the inferior temporal cortex and superior temporal sulcus of two male macaque monkeys. Our findings reveal that mid-level categories are well represented at both LSF and high SF (HSF), suggesting robust mid-level boundary maps in these areas, unaffected by SF changes. Conversely, superordinate category representation depends on HSF, indicating its crucial role in encoding global category information. The absence of subordinate representation in both LSF and HSF compared to intact stimuli further implies that full SF content is essential for fine-category processing. A supporting human psychophysics task confirms that superordinate categorization relies on HSF, while subordinate object recognition requires both LSF and HSF.