Biology subjects

Cardenas, A. R.

Publications and source records attributed to Cardenas, A. R..

3 recordsLinked to original sources

bioRxiv2021

Severe distortion in the representation of foveal visual image locations in short term memory

The foveal visual image region provides the human visual system with the highest acuity. However, it is unclear whether such a high fidelity representational advantage is maintained when foveal image locations are committed to short term memory. Here we describe a paradoxically large distortion in foveal target location recall by humans. We briefly presented small, but high contrast, points of light at eccentricities ranging from 0.1 to 12 deg, while subjects maintained their line of sight on a stable target. After a brief memory period, the subjects indicated the remembered target locations via computer controlled cursors. The biggest localization errors, in terms of both directional deviations and amplitude percentage overshoots or undershoots, occurred for the most foveal targets, and such distortions were still present, albeit with qualitatively different patterns, when subjects shifted their gaze to indicate the remembered target locations. Foveal visual images are severely distorted in short term memory.

neuroscience↗

bioRxiv2020

Differential causal involvement of human auditory and frontal cortices in vocal motor control

Speech motor control requires integration of sensory and motor information. Bidirectional communication between frontal and auditory cortices is crucial for speech production, self-monitoring and motor control. We used cortical direct electrical stimulation (DES) to functionally dissect audio-motor interactions underlying speech production and motor control. Eleven neurosurgical patients performed a visually cued vocal task in which a short auditory feedback perturbation was introduced during vocalization. We evaluated the effect of DES on vocal initiation, voice fundamental frequency (F0) and feedback-dependent motor control. DES of frontal sites modulated vocal onset latencies. Stimulation of different inferior frontal gyrus sites elicited either shortening or prolongation of vocal latencies. DES distinctly modulated voice F0 at different vocalization stages. Frontal and temporal areas played an important role in setting voice F0 in the first 250 ms of an utterance, while Heschls gyrus was involved later when auditory input is available for self-monitoring. Vocal responses to pitch-shifted auditory feedback were mostly reduced by DES of non-core auditory cortices. Overall, we demonstrate that vocal planning and initiation are driven by frontal cortices, while feedback-dependent control relies predominantly on non-core auditory cortices. Our findings represent direct evidence of the role played by different auditory and frontal regions in vocal motor control.

neuroscience↗

bioRxiv2020

Focal cortical surface cooling is a novel and safe method for intraoperative functional brain mapping

ObjectiveElectrical cortical stimulation (ECS) has been the gold standard for intraoperative functional mapping in neurosurgery, yet it carries the risk of induced seizures. Here we assess the safety of focal cortical cooling (CC) as a potential alternative to ECS for functional brain mapping. MethodsWe retrospectively reviewed 40 consecutive subjects (n=13 tumor, 27 mesial temporal lobe epilepsy (MTLE) resection) who underwent intraoperative CC during craniotomy at the University of Iowa Hospital and Clinics from 2007 through 2019 (CC group). Thirty-eight of the 40 subjects had ECS performed along with CC during the same procedure. To assess the safety of CC, intra- and post-operative seizure incidence and post-operative neurological deficits were collected together with new post-operative radiographic findings not related to the surgical procedure itself (i.e. non-mapping portions). As a control cohort, we collected 55 consecutive subjects (n=21 MTLE, 34 tumor/vascular pathology) who underwent awake ECS mapping without CC between 2006 and 2019 (ECS-alone group). To evaluate potential long term effects of mapping techniques (CC and/or ECS), we separately collected another 25 consecutive subjects who underwent anterior temporal lobectomy(ATL) without CC nor ECS between 2007 and 2019 (No ECS/No CC-ATL group). ResultsA total of 79 brain sites were cooled in the 40 CC subjects, including inferior frontal gyrus (44%), precentral gyrus (39%), postcentral gyrus (6%), subcentral gyrus (4%) and superior temporal gyrus (6%). No intraoperative seizures were reported in the CC group, whereas 3.6% of ECS-alone group had intraoperative seizures. The incidence of seizure(s) within the first post-operative week did not significantly differ amongst CC (7.9%), ECS-alone (9.0%) and No ECS/No CC-ATL groups (12%). There was no significante difference in the incidence of postoperative radiographic change between CC (7.5%) and ECS-alone groups (5.5 %). The long term seizure outcome for MTLE subjects did not statistically differ regarding good outcomes (Engel I+II): CC group (80%), ECS-alone (83.3%) and No ECS/No CC-ATL group (83.3%). ConclusionsCortical cooling when used as an intraoperative mapping technique is safe, and may complement traditional electrical cortical stimulation.

neuroscience↗