Trepka, E. B. | bioRxiv Science

bioRxiv2024

Dependence of Contextual Modulation in Macaque V1 on Interlaminar Signal Flow

In visual cortex, neural correlates of subjective perception can be generated by modulation of activity from beyond the classical receptive field (CRF). In macaque V1, activity generated by nonclassical receptive field (nCRF) stimulation involves different intracortical circuitry than activity generated by CRF stimulation, suggesting that interactions between neurons across V1 layers differ under CRF and nCRF stimulus conditions. Using Neuropixels probes, we measured border ownership modulation within large, local populations of V1 neurons. We found that neurons in single columns preferred the same side of objects located outside of the CRF. In addition, we found that cross-correlations between pairs of neurons situated across feedback/horizontal and input layers differed between CRF and nCRF stimulation. Furthermore, independent of the comparison with CRF stimulation, we observed that the magnitude of border ownership modulation increased with the proportion of information flow from feedback/horizontal layers to input layers. These results demonstrate that the flow of signals between layers covaries with the degree to which neurons integrate information from beyond the CRF.

neuroscience↗

bioRxiv2023

Cue-specific neuronal ensembles span intermittent rate coding of working memory

Persistent, memorandum-specific neuronal spiking activity has long been hypothesized to underlie working memory. However, emerging evidence suggests a possible role for activity-silent synaptic mechanisms. This issue remains controversial because evidence for either view has largely depended on datasets that fail to capture single-trial population dynamics or on indirect measures of neuronal spiking. We addressed this by examining the dynamics of mnemonic information on single trials obtained from large, local populations of prefrontal neurons recorded simultaneously in monkeys performing a working memory task. We show that mnemonic information does not persist in the spiking activity of prefrontal neurons, but instead alternates between On and Off periods during memory delays. At the level of single neurons, Off periods are driven by a coordinated loss of selectivity for memoranda and a return of firing rates to baseline levels. Further exploiting the large-scale recordings, we asked whether the functional connectivity among large neuronal ensembles depended on information held in working memory. We show that mnemonic information is available in the pattern of ensemble connectivity during the memory delay in both On and Off periods of neuronal activity. Intermittent epochs of memoranda-specific spiking therefore coexist with activity-silent mechanisms to span memory delays.

neuroscience↗