Biology subjects

Gumenchuk, I.

Publications and source records attributed to Gumenchuk, I..

2 recordsLinked to original sources

bioRxiv2019

Asymmetric, dynamic adaptation in prefrontal cortex during dichotic listening tasks

Speech comprehension relies on highly distributed, dynamically interconnected neuroanatomical loci. Accordingly, performance on complex speech processing tasks such as dichotic listening can be used to assess the integrity and health of many functional and structural aspects of the brain. Despite the potential merits as a clinical assessment tool, however, the neural substrates activated during dichotic listening remain relatively opaque at higher processing levels. Ultimately, this knowledge gap limits diagnostic use of the task. At the level of the prefrontal cortex, dichotic listening induces an asymmetric response wherein regions on the right hemisphere exhibit a higher functional activation than on the left. Superficially, this finding is counterintuitive given the left hemispheres dominance for speech and language. To obtain a more in-depth perspective on the potentially distinct roles of the right and left prefrontal cortex, we optically monitored cerebral blood flow in the dorsolateral prefrontal cortex (DLPFC) during dichotic listening tasks in human subjects. The method permitted us to avoid systematic experimental confounds that functional magnetic resonance imaging (fMRI) measurements suffer from, namely the influence of scanner noise. In addition to reproducing the documented larger activation amplitude in the right hemisphere, we also found that repeated listening task blocks were associated with altered kinetics of blood flow in the right, but not the left DLPFC. Interestingly, subjects with the most prominent regional blood flow changes in the right hemisphere also displayed large distortion product otoacoustic emissions (DPOAEs) in the left ear, possibly signaling a correlation between prefrontal activity and top-down listening control infrastructure through medial olivocochlear efferent projections to the inner ear. Overall, our results suggest that the right prefrontal cortical regions play an active role in optimizing task performance.

neuroscience↗

bioRxiv2017

Low-intensity focused ultrasound alters the latency and spatial patterns of sensory-evoked cortical responses in vivo.

The use of transcranial, low intensity focused ultrasound (FUS) is an emerging neuromodulation technology that shows promise for both therapeutic and research applications. Compared with other noninvasive neuromodulation approaches, key technical advantages include high lateral resolution of stimulation and deep penetration depth. However, empirically observed effects in vivo are diverse; for example, variations in sonication location and waveform can alternatively elicit putatively inhibitory or excitatory effects. At a fundamental level, it is unclear how FUS alters the function of neural circuits at the site of sonication. To address this knowledge gap, we developed an approach to optically interrogate the spatiotemporal patterns of neural activity in the cortex directly at the acoustic focus, thereby offering a glimpse into the local effects of FUS on distributed populations of neurons in vivo. Our experiments probed electrical activity through the use of voltage sensitive dyes (VSDs) and, in transgenic GCaMP6f mice, monitored associated Ca2+ responses. Our results directly demonstrate that low-intensity FUS adjusts both the kinetics and spatial patterns of sensory receptive fields at the acoustic focus in vivo. Although our experimental configuration limits interpretation to population activity, the use of VSDs ensures that the detected alterations reflect activity in cortical neurons, unobscured by signals in subcortical or laterally distant cortical regions. More generally, this optical measurement paradigm can be implemented to observe FUS-induced alterations in cortical representation with higher lateral resolution spatial versatility than is practical through more conventional electrodebased measurements. Our findings suggest that reports of FUS-induced sensory modulation in human studies may partly reflect alterations cortical representation and reactivity.

neuroscience↗