scholarly journals Multiple states in ongoing neural activity in the rat visual cortex

PLoS ONE ◽  
2021 ◽  
Vol 16 (8) ◽  
pp. e0256791
Author(s):  
Daichi Konno ◽  
Shinji Nishimoto ◽  
Takafumi Suzuki ◽  
Yuji Ikegaya ◽  
Nobuyoshi Matsumoto
Keyword(s):  
Visual Cortex ◽  
Neural Activity ◽  
Activity Patterns ◽  
Electrode Array ◽  
Nonlinear Dimensionality Reduction ◽  
Neural Responses ◽  
Spontaneous Neural Activity ◽  
Custom Made ◽  
Visual Cortices ◽  
Freely Behaving

The brain continuously produces internal activity in the absence of afferently salient sensory input. Spontaneous neural activity is intrinsically defined by circuit structures and associated with the mode of information processing and behavioral responses. However, the spatiotemporal dynamics of spontaneous activity in the visual cortices of behaving animals remain almost elusive. Using a custom-made electrode array, we recorded 32-site electrocorticograms in the primary and secondary visual cortex of freely behaving rats and determined the propagation patterns of spontaneous neural activity. Nonlinear dimensionality reduction and unsupervised clustering revealed multiple discrete states of the activity patterns. The activity remained stable in one state and suddenly jumped to another state. The diversity and dynamics of the internally switching cortical states would imply flexibility of neural responses to various external inputs.

scholarly journals Spontaneous Neural Activity Changes after Bariatric Surgery: a resting-state fMRI study

2021 ◽  
Author(s):  
Yashar Zeighami ◽  
Sylvain Iceta ◽  
Mahsa Dadar ◽  
Mélissa Pelletier ◽  
Mélanie Nadeau ◽  
...  
Keyword(s):  
Bariatric Surgery ◽  
Weight Loss ◽  
Visual Cortex ◽  
Neural Activity ◽  
Dorsolateral Prefrontal Cortex ◽  
Severe Obesity ◽  
Normal Weight ◽  
Post Surgery ◽  
Spontaneous Neural Activity ◽  
Dorsolateral Prefrontal

1.AbstractBackgroundMetabolic disorders associated with obesity could lead to alterations in brain structure and function. Whether these changes can be reversed after weight loss is unclear. Bariatric surgery provides a unique opportunity to address these questions because it induces marked weight loss and metabolic improvements which in turn may impact the brain in a longitudinal fashion. Previous studies found widespread changes in grey matter (GM) and white matter (WM) after bariatric surgery. However, findings regarding changes in spontaneous neural activity following surgery, as assessed with the fractional amplitude of low frequency fluctuations (fALFF) and regional homogeneity of neural activity (ReHo), are scarce and heterogenous. In this study, we used a longitudinal design to examine the changes in spontaneous neural activity after bariatric surgery (comparing pre- to post-surgery), and to determine whether these changes are related to cardiometabolic variables.MethodsThe study included 57 participants with severe obesity (mean BMI=43.1±4.3kg/m2) who underwent sleeve gastrectomy (SG), biliopancreatic diversion with duodenal switch (BPD), or Roux-en-Y gastric bypass (RYGB), scanned prior to bariatric surgery and at follow-up visits of 4 months (N=36), 12 months (N=29), and 24 months (N=14) after surgery. We examined fALFF and ReHo measures across 1022 cortical and subcortical regions (based on combined Schaeffer-Xiao parcellations) using a linear mixed effect model. Voxel-based morphometry (VBM) based on T1-weighted images was also used to measure GM density in the same regions. We also used an independent sample from the Human Connectome Project (HCP) to assess regional differences between individuals who had normal-weight (N=46) or severe obesity (N=46).ResultsWe found a global increase in the fALFF signal with greater increase within dorsolateral prefrontal cortex, precuneus, inferior temporal gyrus, and visual cortex. This effect was more significant 4 months after surgery. The increase within dorsolateral prefrontal cortex, temporal gyrus, and visual cortex was more limited after 12 months and only present in the visual cortex after 24 months. These increases in neural activity measured by fALFF were also significantly associated with the increase in GM density following surgery. Furthermore, the increase in neural activity was significantly related to post-surgery weight loss and improvement in cardiometabolic variables, such as insulin resistance index and blood pressure. In the independent HCP sample, normal-weight participants had higher global and regional fALFF signals, mainly in dorsolateral/medial frontal cortex, precuneus and middle/inferior temporal gyrus compared to the obese participants. These BMI-related differences in fALFF were associated with the increase in fALFF 4 months post-surgery especially in regions involved in control, default mode and dorsal attention networks.ConclusionsBariatric surgery-induced weight loss and improvement in metabolic factors are associated with widespread global and regional increases in neural activity, as measured by fALFF signal. These findings alongside the higher fALFF signal in normal-weight participants compared to participants with severe obesity in an independent dataset suggest an early recovery in the neural activity signal level after the surgery.

scholarly journals Naturalistic audio-movies reveal common spatial organization across “visual” cortices of different blind individuals

2021 ◽  
Author(s):  
Elizabeth Musz ◽  
Rita Loiotile ◽  
Janice Chen ◽  
Marina Bedny
Keyword(s):  
Visual Cortex ◽  
Visual Information ◽  
Spatial Organization ◽  
Activity Patterns ◽  
Auditory Stimuli ◽  
Spatial Activity ◽  
Pattern Similarity ◽  
Congenitally Blind ◽  
Visual Cortices ◽  
Blind Individuals

AbstractOccipital cortices of different sighted people contain analogous maps of visual information (e.g., foveal vs. peripheral space). In congenital blindness, “visual” cortices enhance responses to nonvisual stimuli. Do deafferented visual cortices of different blind people represent common informational maps? We leverage a naturalistic stimulus paradigm and inter-subject pattern similarity analysis to address this question. Blindfolded sighted (S, n=22) and congenitally blind (CB, n=22) participants listened to three auditory excerpts from movies; a naturalistic spoken narrative; and matched degraded auditory stimuli (i.e., shuffled sentences and backwards speech) while undergoing fMRI scanning. In a parcel-based whole brain analysis, we measured the spatial activity patterns evoked by each unique, ten-second segment of each auditory clip. We then compared each subject’s spatial pattern to that of all other subjects in the same group (CB or S) within and across segments. In both blind and sighted groups, segments of meaningful auditory stimuli produced distinctive patterns of activity that were shared across individuals. Crucially, only in the CB group, this segment-specific, cross-subject pattern similarity effect emerged in visual cortex, but only for meaningful naturalistic stimuli and not backwards speech. These results suggest that spatial activity patterns within deafferented visual cortices encode meaningful, segment-level information contained in naturalistic auditory stimuli, and that these representations are spatially organized in a similar fashion across blind individuals.Significance StatementRecent neuroimaging studies show that the so-called “visual” cortices activate during non-visual tasks in people who are born blind. Do the visual cortices of people who are born blind develop similar representational maps? While congenitally blind individuals listened to naturalistic auditory stimuli (i.e., sound clips from movies), distinct timepoints within each stimulus elicited unique spatial activity patterns in visual cortex, and these patterns were shared across different people. These findings suggest that in blindness, the visual cortices encode meaningful information embedded in naturalistic auditory signals in a spatially distributed manner, and that a common representational map can emerge in visual cortex independent of visual experience.

scholarly journals Categorical working memory codes in human visual cortex

2021 ◽  
Author(s):  
Chang Yan ◽  
Thomas B. Christophel ◽  
Carsten Allefeld ◽  
John-Dylan Haynes
Keyword(s):  
Working Memory ◽  
Visual Cortex ◽  
Neural Activity ◽  
Activity Patterns ◽  
Levels Of Abstraction ◽  
Cortical Hierarchy ◽  
Multiple Regions ◽  
Memory Contents ◽  
Memory Codes ◽  
Different Levels

Working memory contents are represented in neural activity patterns across multiple regions of the cortical hierarchy. It has remained unclear to which degree this reflects a specialization for different levels of abstraction. Here, we demonstrate that for color stimuli categorical codes are already present at the level of extrastriate visual cortex (V4 and VO1). Importantly, this categorical coding was observed during working memory, but not during perception.

scholarly journals Direction-selective motion discrimination by traveling waves in visual cortex

2020 ◽  
Author(s):  
Stewart Heitmann ◽  
G. Bard Ermentrout
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Primary Visual Cortex ◽  
Visual Stimulus ◽  
Traveling Waves ◽  
Neural Activity ◽  
Time Delays ◽  
Neural Mechanism ◽  
Neural Responses ◽  
Transmission Delays

AbstractThe majority of neurons in primary visual cortex respond selectively to bars of light that have a specific orientation and move in a specific direction. The spatial and temporal responses of such neurons are non-separable. How neurons accomplish that computational feat without resort to explicit time delays is unknown. We propose a novel neural mechanism whereby visual cortex computes non-separable responses by generating endogenous traveling waves of neural activity that resonate with the space-time signature of the visual stimulus. The spatiotemporal characteristics of the response are defined by the local topology of excitatory and inhibitory lateral connections in the cortex. We simulated the interaction between endogenous traveling waves and the visual stimulus using spatially distributed populations of excitatory and inhibitory neurons with Wilson-Cowan dynamics and inhibitory-surround coupling. Our model reliably detected visual gratings that moved with a given speed and direction provided that we incorporated neural competition to suppress false motion signals in the opposite direction. The findings suggest that endogenous traveling waves in visual cortex can impart direction-selectivity on neural responses without resort to explicit time delays. They also suggest a functional role for motion opponency in eliminating false motion signals.Author summaryIt is well established that the so-called ‘simple cells’ of the primary visual cortex respond preferentially to oriented bars of light that move across the visual field with a particular speed and direction. The spatiotemporal responses of such neurons are said to be non-separable because they cannot be constructed from independent spatial and temporal neural mechanisms. Contemporary theories of how neurons compute non-separable responses typically rely on finely tuned transmission delays between signals from disparate regions of the visual field. However the existence of such delays is controversial. We propose an alternative neural mechanism for computing non-separable responses that does not require transmission delays. It instead relies on the predisposition of the cortical tissue to spontaneously generate spatiotemporal waves of neural activity that travel with a particular speed and direction. We propose that the endogenous wave activity resonates with the visual stimulus to elicit direction-selective neural responses to visual motion. We demonstrate the principle in computer models and show that competition between opposing neurons robustly enhances their ability to discriminate between visual gratings that move in opposite directions.

Spontaneous neural activity in the primary visual cortex of retinal degenerated rats

2016 ◽  
Vol 623 ◽  
pp. 42-46 ◽  
Author(s):  
Yi Wang ◽  
Ke Chen ◽  
Ping Xu ◽  
Tsz Kin Ng ◽  
Leanne Lai Hang Chan
Keyword(s):  
Visual Cortex ◽  
Primary Visual Cortex ◽  
Neural Activity ◽  
Spontaneous Neural Activity

scholarly journals Insula activity in resting-state differentiates bipolar from unipolar depression: a systematic review and meta-analysis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Martin Pastrnak ◽  
Eva Simkova ◽  
Tomas Novak
Keyword(s):  
Neural Activity ◽  
Resting State ◽  
Meta Analysis ◽  
Activity Patterns ◽  
Likelihood Estimation ◽  
Unipolar Depression ◽  
Adjacent Area ◽  
Spontaneous Neural Activity ◽  
Therapeutic Problem ◽  
Depressive Episodes

AbstractSymptomatic overlap of depressive episodes in bipolar disorder (BD) and major depressive disorder (MDD) is a major diagnostic and therapeutic problem. Mania in medical history remains the only reliable distinguishing marker which is problematic given that episodes of depression compared to episodes of mania are more frequent and predominantly present at the beginning of BD. Resting-state functional magnetic resonance imaging (rs-fMRI) is a non-invasive, task-free, and well-tolerated method that may provide diagnostic markers acquired from spontaneous neural activity. Previous rs-fMRI studies focused on differentiating BD from MDD depression were inconsistent in their findings due to low sample power, heterogeneity of compared samples, and diversity of analytical methods. This meta-analysis investigated resting-state activity differences in BD and MDD depression using activation likelihood estimation. PubMed, Web of Science, Scopus and Google Scholar databases were searched for whole-brain rs-fMRI studies which compared MDD and BD currently depressed patients between Jan 2000 and August 2020. Ten studies were included, representing 234 BD and 296 MDD patients. The meta-analysis found increased activity in the left insula and adjacent area in MDD compared to BD. The finding suggests that the insula is involved in neural activity patterns during resting-state that can be potentially used as a biomarker differentiating both disorders.

scholarly journals Zero-shot neural decoding of visual categories without prior exemplars

2019 ◽  
Author(s):  
Thomas P. O’Connell ◽  
Marvin M. Chun ◽  
Gabriel Kreiman
Keyword(s):  
Neural Network ◽  
Visual Cortex ◽  
Neural Activity ◽  
Deep Neural Network ◽  
Temporal Cortex ◽  
Inferior Temporal Cortex ◽  
Neural Decoding ◽  
Neural Responses ◽  
Prior Training ◽  
Single Category

AbstractDecoding information from neural responses in visual cortex demonstrates interpolation across repetitions or exemplars. Is it possible to decode novel categories from neural activity without any prior training on activity from those categories? We built zero-shot neural decoders by mapping responses from macaque inferior temporal cortex onto a deep neural network. The resulting models correctly interpreted responses to novel categories, even extrapolating from a single category.

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