Biology subjects

Agayby, B.

Publications and source records attributed to Agayby, B..

4 recordsLinked to original sources

bioRxiv2026

Ordinal position in auditory sequences is encoded in population dynamics in macaque frontal cortex

The ability to extract structure from sensory sequences requires tracking not only stimulus identity but also ordinal position within a sequence. How and where ordinal information is represented in the primate brain remains unclear. Here, we recorded activity in populations of single neurons simultaneously from auditory cortex and ventrolateral prefrontal cortex in macaques passively listening to structured auditory sequences. Population-level analyses revealed that frontal cortex activity evolved progressively across the sequence, occupying distinct regions of neural state space for successive ordinal positions. In contrast, auditory cortex population activity reset with each element, producing stereotyped, stimulus-locked trajectories. Consistent with this dissociation, frontal cortex populations robustly decoded ordinal position independently of stimulus identity, whereas auditory cortex showed weak positional decoding despite strong identity representations. Frontal neurons further exhibited longer intrinsic timescales and reduced synchronization to element presentation, supporting integration of information across multiple elements. Together, these findings identify frontal activity as a key substrate for ordinal position encoding during auditory sequence processing, while auditory cortex primarily supports element-specific sensory representations.

neuroscience↗

bioRxiv2021

Stimulus dependence of theta rhythmic activity in primate V1 and its potential relevance for visual perception

Theta-band (3-8 Hz) neural oscillations are integral to sensory processing and active exploration. Traditionally associated with higher-order areas such as hippocampus and prefrontal cortex, recent studies identified theta rhythmic modulations in the primary visual cortex (V1) of mice during locomotion, suggesting sensory processing functions. Here, we demonstrate that careful optimization of visual stimulus size and contrast can induce robust theta oscillations in macaque V1. During visual detection, monkeys reaction times fluctuated rhythmically at the theta frequency of V1 neural activity, with detection performance correlated to the theta phase. These findings suggest that induced theta oscillations may reflect an intrinsic temporal filtering mechanism of V1 neurons, highlighting the importance of early sensory cortical dynamics in shaping perceptual timing.

neuroscience↗

bioRxiv2021

Optogenetic stimulation of primate V1 reveals local laminar and large-scale cortical networks related to perceptual phosphenes

Developing optogenetics in non-human primates (NHPs) is essential for translating its successful implementation in rodents to clinical applications in humans. However, information about how optogenetics influences the primate cortex remains limited. Here, we evaluate how optogenetic stimulation of the primate primary visual cortex (V1) affects local and large-scale network activation concerned with visual perception. To this end we injected an optogenetic construct (AAV9-hSyn-ChR2-eYFP) into the V1 cortex of four macaque monkeys (macaca mulatta) and measured the effects of optogenetic V1 stimulation using functional magnetic resonance imaging (fMRI), laminar electrophysiology, and behavioural assessment. In three macaques, blood-oxygen-dependent (BOLD) fMRI activity could be reliably elicited with optogenetic stimulation in V1 and several connected extrastriate brain areas, including V2/V3, motion-sensitive area MT and the frontal-eye-fields (FEF), in particular when pulsed stimulation at 40 Hz was applied. BOLD modulation was associated with consistent neural spiking activity measured in V1 of two macaques. More detailed analysis revealed strongest neuronal activation in layer 4B and infragranular layers, which tightly reflected the histological expression pattern of the optogenetic construct in V1. Driving this visual network proved sufficient to elicit a visual percept ( phosphene) in one macaque during a perceptual choice task. Taken together, our findings reveal the laminar and large-cortical activation pattern related to visual phosphene generation and emphasize the need for further improving optogenetic methods in NHPs as a step towards applications in humans.

neuroscience↗

bioRxiv2017

Extra-field spike-timed activity shifts the place field center of mass to encode aversion experience

The hippocampal place cells encode spatial representation but it remains unclear how they store concurrent positive or negative experiences. Here, we report on place field reconfiguration in response to an innately aversive odor trimethylthiazoline (TMT). The advantage of TMT is the absence of learning curve required for associative fear conditioning. Our study investigated if CA1 place cells, recorded from behaving rats, remap randomly or if their reconfiguration depends on the location of the aversive stimulus perception. Exposure to TMT increased the amplitude of hippocampal beta oscillations in two arms of a maze (TMT arms). We found that a population of place cells with fields located outside the TMT arms increased their activity (extra-field spiking) in the TMT arms during the aversive episodes. These cells exhibited significant shift of the center of mass towards the TMT arms in the subsequent post-TMT recording. The induction of extra-field plasticity was mediated by the basolateral amygdala complex (BLA). Photostimulation of the BLA triggered aversive behavior, synchronized response of hippocampal local field oscillations, augmented theta rhythm amplitude and increased the spiking of place cells for the first 100ms after the light delivery. This occurred only for the extra-field-but not for intra-field spikes. Optogenetic BLA-triggered an increase in extra-field spiking activity correlated to the degree of place field plasticity in the post-ChR2 recording session. Our findings demonstrate that the increased extra-field activity during aversive episodes mediates the degree of subsequent field plasticity.

neuroscience↗