Biology subjects

Nurminen, L.

Publications and source records attributed to Nurminen, L..

4 recordsLinked to original sources

bioRxiv2026

Parvalbumin-expressing interneurons improve sensory discrimination by shaping noise geometry in primate V1

The ability to discriminate sensory stimuli is fundamental to sensory-guided behavior. Sensory discrimination by neural populations is constrained by the magnitude of trial-to-trial spiking variability, or noise, and its geometric alignment with the stimulus encoding directions of the population response. Computational models predict that cortical inhibition shapes the noise geometry, but causal evidence from primate cortex is lacking. We used optogenetic stimulation of parvalbumin-expressing inhibitory interneurons (PV-cells) combined with high-density extracellular recordings in primary visual cortex of awake marmoset monkeys to test this prediction. Stimulating PV-cells improved the discriminability of V1 population responses, without expanding the stimulus-related signal magnitude. Instead, PV-cell activation compressed shared trial-to-trial variability and rotated it away from the stimulus-coding direction. Our results establish a causal role for inhibition in shaping the geometry of neural population responses to improve sensory discrimination in the primate visual cortex.

neuroscience↗

bioRxiv2023

Size tuning of neural response variability in laminar circuits of macaque primary visual cortex

Surround suppression and neural response variability are two widespread cortical phenomena thought to facilitate and impede, respectively, information processing and perception. Typically, manipulations that elicit neural response suppression quench variability, an observation that has led some to suggest that these two phenomena may share a common origin. However, few studies have systematically examined the relationship between surround suppression and variability. Surround suppression is mediated by multiple circuits and mechanisms that depend on the size of the sensory stimulus, and cortical layer. Variability is also laminar dependent. To understand how surround suppression and variability may influence laminar processing, here we have used electrophysiological laminar recordings to examine how neural response variability and the shared variability among neurons are modulated by visual stimulus size across the layers of macaque primary visual cortex (V1). We find that surround suppression does not always quench variability. Instead, variability is tuned for stimulus size in a layer-dependent manner. In all layers, stimulation of the receptive field (RF) reduced neural response variability, and the shared variability among neurons, relative to their pre-stimulus values. As the stimulus was enlarged beyond the RF, to involve the near RF-surround, both neural response variability and shared variability further decreased in infragranular layers, but did not change in granular and supragranular layers. In contrast, larger stimuli involving the far RF-surround increased both neural response variability and shared variability, relative to their value for a stimulus matched to the RF size, in supragranular layers, but decreased them or did not change them in granular and infragranular layers. Surprisingly, we also found that visual stimuli smaller than the RF could increase variability relative to baseline values, particularly in granular and infragranular layers. Our results point to multiple laminar-specific circuits and mechanisms as the source of variability, and call for new models of neural response variability.

neuroscience↗

bioRxiv2017

Distinct Laminar Processing of Local and Global Context in Primate Primary Visual Cortex

Visual perception is profoundly affected by spatial context. In visual cortex, neuronal responses to stimuli inside their receptive field (RF) are suppressed by contextual stimuli in the RF surround (surround suppression). How do neuronal RFs integrate information across visual space, and what role do different cortical layers play in the processing of spatial context? By recording simultaneously across all layers of macaque primary visual cortex, while presenting visual stimuli at increasing distances from the recorded cells RF, we find that near vs. far stimuli activate distinct layers. Stimuli in the near-surround evoke the earliest subthreshold responses in superficial and deep layers, and cause the earliest surround suppression of spiking responses in superficial layers. Instead, far-surround stimuli evoke the earliest subthreshold responses in feedback-recipient layers, i.e. 1 and the lower half of the deep layers, and suppress visually-evoked spiking responses almost simultaneously in all layers, except 4C, where suppression emerges latest. Our results reveal unique contributions of the cortical layers to the processing of local and global spatial context, and suggest distinct underlying circuits for local and global signal integration.

neuroscience↗

bioRxiv2016

CORTICO-CORTICAL FEEDBACK CONTROLS SPATIAL SUMMATION IN PRIMATE VISUAL CORTEX

In the cerebral cortex, sensory information travels along feedforward connections through a hierarchy of areas, which, in turn, send a denser network of feedback connections to lower-order areas. Feedback has been implicated in attention, expectation, and sensory context, but the cellular mechanisms underlying these diverse feedback functions are unknown. Using specific optogenetic inactivation of feedback connections in the primate visual cortex, we have identified the cellular mechanisms of feedback-mediated modulations of early sensory processing. Specifically, we found that feedback modulates receptive field size, surround suppression and response gain, similar to the modulatory effects of visual spatial attention. A recurrent network model captured these effects. These feedback-mediated modulations allow higher-order cortical areas to dynamically regulate spatial resolution, sensitivity to image features, and efficiency of coding natural images in lower-order cortical areas.

neuroscience↗