Rodents' visual gamma as a biomarker of pathological neural conditions

Neural gamma oscillations (indicatively 30-100 Hz) are ubiquitous: they are associated with a broad range of functions in multiple cortical areas and across many animal species. Experimental and computational works established gamma rhythms as a global emergent property of neuronal networks generated by the balanced and coordinated interaction of excitation and inhibition. Coherently, gamma activity is strongly influenced by the alterations of synaptic dynamics which are often associated with pathological neural dysfunctions. We argue therefore that these oscillations are an optimal biomarker for probing the mechanism of cortical dysfunctions. Gamma oscillations are also highly sensitive to external stimuli in sensory cortices, especially the primary visual cortex (V1), where the stimulus dependence of gamma oscillations has been thoroughly investigated. Gamma manipulation by visual stimuli tuning is particularly easy in rodents, which have become a standard animal model for investigating the effects of network alterations on gamma oscillations. Overall, gamma in the rodents' visual cortex offers an accessible probe on dysfunctional information processing in pathological conditions. Beyond vision-related dysfunctions, alterations of gamma oscillations in rodents were indeed also reported in neural deficits such as migraine, epilepsy and neurodegenerative or neuropsychiatric conditions such as Alzheimer's, schizophrenia and autism spectrum disorders. Altogether, the connections between visual cortical gamma activity and physio-pathological conditions in rodent models underscore the potential of gamma oscillations as markers of neuronal (dys)functioning. image Abstract figure legend Cortical processing of visual information can be investigated through the magnifying lens of gamma oscillations. Given their sensitivity to multiple circuit dysfunctions, gamma oscillations in the visual cortex can crucially also serve as a biomarker for probing dysfunctional information processing in multiple pathological conditions. We summarize the fundamental circuit mechanisms underlying gamma oscillations, with a particular emphasis on the unique characteristics of gamma oscillations in the visual cortex of rodents. Furthermore, we review recent findings that underscore the connection between gamma rhythm alterations in a rodent's visual cortex and several diseases, including epilepsy, migraine, schizophrenia, fragile X syndrome and Alzheimer's disease. image