Biomedical subjects

Scott D Slotnick

Publications and source records attributed to Scott D Slotnick.

23 records · Page 2Linked to original sources

PubMed2003

Model fitting in (n+1) dimensions.

Conventionally, fitting a mathematical model to empirically derived data is achieved by varying model parameters to minimize the deviations between expected and observed values in the dependent dimension. However, when functions to be fit are multivalued (e.g., an ellipse), conventional model fitting procedures fail. A novel (n+1)-dimensional [(n+1)-D] model fitting procedure is presented which can solve such problems by transforming the n-D model and data into (n+1)-D space and then minimizing deviations in the constructed dimension. While the (n+1)-D procedure provides model fits identical to those obtained with conventional methods for single-valued functions, it also extends parameter estimation to multivalued functions.

Algorithms↗

PubMed2002

Darkness beyond the light: attentional inhibition surrounding the classic spotlight.

The aim of the present investigation was to determine the nature and spatial distribution of selective visual attention. Using cortical source localization of ERP data corresponding to 60 task-irrelevant stimuli across the visual field, we assessed attention effects on visual processing. Consistent with previous findings, visual processing was enhanced at the attended spatial location. In addition, this facilitation of processing extended from the attended location to the point of fixation resulting in a region of facilitation. Furthermore, a large region of inhibition was found surrounding this region of facilitation. The latter result is inconsistent with a simple facilitative spotlight model of attention and indicates that attention effects can be both facilitatory and inhibitory.

Adult↗

PubMed2002

Interactions between thalamic and cortical rhythms during semantic memory recall in human.

Human scalp electroencephalographic rhythms, indicative of cortical population synchrony, have long been posited to reflect cognitive processing. Although numerous studies employing simultaneous thalamic and cortical electrode recording in nonhuman animals have explored the role of the thalamus in the modulation of cortical rhythms, direct evidence for thalamocortical modulation in human has not, to our knowledge, been obtained. We simultaneously recorded from thalamic and scalp electrodes in one human during performance of a cognitive task and found a spatially widespread, phase-locked, low-frequency rhythm (7-8 Hz) power decrease at thalamus and scalp during semantic memory recall. This low-frequency rhythm power decrease was followed by a spatially specific, phase-locked, fast-rhythm (21-34 Hz) power increase at thalamus and occipital scalp. Such a pattern of thalamocortical activity reflects a plausible neural mechanism underlying semantic memory recall that may underlie other cognitive processes as well.

Brain Mapping↗

PubMed2002

A prospective study of motor recovery following multiple subpial transections.

A prospective study of motor recovery was undertaken in a patient scheduled to undergo multiple subpial transections (MST) of right sensorimotor cortex. Pre-transection, functional MRI (fMRI) and cortical stimulation mapping confirmed left hand motor control within right primary motor cortex. Immediately post-transection, behavioral testing demonstrated preserved strength bilaterally but decreased dexterity in the left hand. Seven weeks post-transection, dexterity returned to normal and left hand finger tapping corresponded with multiple bilateral foci of fMRI activation. At 16 weeks, fMRI activation returned to pre-transection levels. These data indicate that cortical injury due to MST resulted in the temporary recruitment of distant cortical sites which presumably subserved normal motor function during recovery.

Adult↗

PubMed2002

Large-scale cortical displacement of a human retinotopic map.

The aim of the current study was to determine the retinotopic organization of a patient with congenital cortical dysgenesis and normal visual function. Using functional magnetic resonance imaging (fMRI), detailed retinotopic maps corresponding to the four visual field quadrants were projected onto cortical surfaces. Similar to control subjects, the upper right visual field mapped onto ventral left hemisphere and was retinotopically organized. The lower right visual field's cortical representation was also retinotopically organized, yet was displaced many centimeters anteriomedially. Moreover, the entire left visual field was represented in non-retinotopically organized islands in both hemispheres. These results indicate retinotopic maps can shift in both location and topography illustrating cortical reorganization presumably due to either cortical dysgenesis or functional displacement. NeuroReport

Adult↗