Biomedical subjects

Jeremy B Caplan

Publications and source records attributed to Jeremy B Caplan.

3 recordsLinked to original sources

PubMed2003

Cellular networks underlying human spatial navigation.

Place cells of the rodent hippocampus constitute one of the most striking examples of a correlation between neuronal activity and complex behaviour in mammals. These cells increase their firing rates when the animal traverses specific regions of its surroundings, providing a context-dependent map of the environment. Neuroimaging studies implicate the hippocampus and the parahippocampal region in human navigation. However, these regions also respond selectively to visual stimuli. It thus remains unclear whether rodent place coding has a homologue in humans or whether human navigation is driven by a different, visually based neural mechanism. We directly recorded from 317 neurons in the human medial temporal and frontal lobes while subjects explored and navigated a virtual town. Here we present evidence for a neural code of human spatial navigation based on cells that respond at specific spatial locations and cells that respond to views of landmarks. The former are present primarily in the hippocampus, and the latter in the parahippocampal region. Cells throughout the frontal and temporal lobes responded to the subjects' navigational goals and to conjunctions of place, goal and view.

Action Potentials↗

PubMed2003

Human theta oscillations related to sensorimotor integration and spatial learning.

oscillations in the rat hippocampus have been implicated in sensorimotor integration (Bland, 1986), especially during exploratory and wayfinding behavior. We propose that human cortical activity coordinates sensory information with a motor plan to guide wayfinding behavior to known goal locations. To test this hypothesis, we analyzed invasive recordings from epileptic patients while they performed a spatially immersive, virtual taxi driver task. Consistent with this hypothesis, we found oscillations during both exploratory search and goal-seeking behavior and, in particular, during virtual movement, when sensory information and motor planning were both in flux, compared with periods of self-initiated stillness. oscillations had different topographic and spectral characteristics during searching than during goal-seeking, suggesting that different cortical networks exhibit depending on which cognitive functions are driving behavior (spatial learning during exploration vs orienting to a learned representation during goal-seeking). In contrast, oscillations in the beta band appeared to be related to simple motor planning, likely a variant of the Rolandic mu rhythm. These findings suggest that human cortical oscillations act to coordinate sensory and motor brain activity in various brain regions to facilitate exploratory learning and navigational planning.

Adolescent↗

PubMed2002

Associative asymmetry in probed recall of serial lists.

For pairs of meaningful items (e.g., words), recall accuracy is nearly identical for forward and backward probes. That is, after studying an A-B pair, subjects can recall A given B as well as they can recall B given A (Kahana, 2002). To assess whether this symmetry property is unique to pairs, we investigated the effects of study direction on probed recall of word triples and serial lists. Two experiments revealed a forward-recall advantage in both triples and serial lists. In addition, compound cues produced better recall than did single-item adjacent cues, which, in turn, produced better recall than did remote cues. These findings suggest a discontinuity between the associative processes supporting memory for pairs and those supporting memory for sequences of three or more items.

Association↗