Biology subjects

Cadena-Valencia, J.

Publications and source records attributed to Cadena-Valencia, J..

3 recordsLinked to original sources

bioRxiv2026

Comparable phosphene size and contrast properties, but differing detection reliability for optogenetic versus electrical stimulation of macaque V1

Cortical visual prostheses aim to restore vision by stimulating primary visual cortex (V1) to evoke artificial percepts (phosphenes). Electrical stimulation has long served this purpose, and optogenetic approaches promise higher spatial resolution via cell-type specificity. Recent investigations have demonstrated localized behavioral responses to optogenetic V1 stimulation (1--3), but the applied perimetry paradigms cannot dissociate a genuine percept from a reflexive oculomotor response, leaving the perceptual character of optogenetic phosphenes unresolved. To address this gap, two macaques received optogenetic V1 injections guided by laminar electrophysiology and performed detection and discrimination tasks under interleaved electrical, optogenetic, and visual stimulation, enabling direct within-subject comparison. Electrical stimulation reliably evoked detectable percepts (positive d' in 100% of sessions), with thresholds scaling with current, resembling visual contrast-response functions. Optogenetic stimulation was far less reliable, with positive d' in only ~50% of sessions, despite confirmed V1 activation. Despite this reliability difference, optogenetically evoked percepts closely resembled electrically and visually evoked percepts in perceptual character: perceived size (~1{degrees} of visual angle) was comparable across conditions and scaled similarly with eccentricity. Similarly, perceived contrast equivalents (5%-11% visual-contrast equivalent) were broadly comparable across stimulation approaches. These findings indicate that successful optogenetic activation engages the same perceptual encoding mechanisms as electrical and natural vision, but that reliable detection may additionally depend on circuit-level mechanisms not consistently engaged by current optogenetic parameters. The comparable percept size further suggests optogenetic stimulation may not confer the enhanced spatial resolution often proposed as its key advantage.

neuroscience↗

bioRxiv2022

Keeping time and rhythm by replaying a sensory-motor engram

Imagine practicing a piece of music, or a speech, solely within the mind, without any sensory input or motor output. Our ability to implement dynamic internal representations is key for successful behavior, yet how the brain achieves this is not fully understood1-4. Here we trained primates to perceive, and internally maintain, rhythms of different tempos and performed large-scale recordings of neuronal activity across multiple areas spanning the sensory-motor processing hierarchy. Results show that perceiving and maintaining rhythms engage multiple brain areas, including visual, parietal, premotor, prefrontal, and hippocampal regions. Each area displayed oscillatory activity that reflected the temporal and spatial characteristics of an internal metronome which flexibly encoded fast, medium, and slow tempos on a trial-by-trial basis. The presence of widespread metronome-related activity across the brain, in the absence of stimuli and overt actions, is consistent with the idea that time and rhythm are maintained by a mechanism that internally replays the stimuli and actions that define well-timed behavior.

neuroscience↗

bioRxiv2018

Entrainment and maintenance of an internal metronome in premotor cortex

To prepare timely motor actions we constantly predict future events. Regularly repeating events are often perceived as a rhythm to which we can readily synchronize our movements, just as in dancing to music. However, the neuronal mechanisms underlying the capacity to encode and maintain rhythms are not understood. We trained nonhuman primates to maintain the rhythm of a visual metronome of different tempos and then we recorded neural activity in the supplementary motor area (SMA). SMA exhibited rhythmic bursts of gamma band (30-40 Hz) reflecting an internal tempo that matched the extinguished visual metronome. Moreover, gamma amplitude increased throughout the trial and provided an estimate of total elapsed time. Notably, the timing and amplitude of gamma bursts reflected systematic timing biases and errors in the behavioral responses. Our results indicate that premotor areas use dynamic motor plans to encode a metronome for rhythms and a stopwatch for total elapsed time.

neuroscience↗