Biomedical subjects

Gina R Poe

Publications and source records attributed to Gina R Poe.

5 recordsLinked to original sources

PubMed2006

Input source and strength influences overall firing phase of model hippocampal CA1 pyramidal cells during theta: relevance to REM sleep reactivation and memory consolidation.

In simulation studies using a realistic model CA1 pyramidal cell, we accounted for the shift in mean firing phase from theta cycle peaks to theta cycle troughs during rapid-eye movement (REM) sleep reactivation of hippocampal CA1 place cells over several days of growing familiarization with an environment (Brain Res 855:176-180). Changes in the theta drive phase and amplitude between proximal and distal dendritic regions of the cell modulated the theta phase of firing when stimuli were presented at proximal and distal dendritic locations. Stimuli at proximal dendritic sites (proximal to 100 microm from the soma) invoked firing with a significant phase preference at the depolarizing theta peaks, while distal stimuli (>290 microm from the soma) invoked firing at hyperpolarizing theta troughs. The input location-related phase preference depended on active dendritic conductances, a sufficient electrotonic separation between input sites and theta-induced subthreshold membrane potential oscillations in the cell. The simulation results predict that the shift in mean theta phase during REM sleep cellular reactivation could occur through potentiation of distal dendritic (temporo-ammonic) synapses and depotentiation of proximal dendritic (Schaffer collateral) synapses over the course of familiarization.

Algorithms↗

PubMed2005

REM restriction persistently alters strategy used to solve a spatial task.

We tested the hypothesis that rapid eye movement (REM) sleep is important for complex associative learning by restricting rats from entering REM sleep for 4 h either immediately after training on an eight-box spatial task (0-4 REMr) or 4 h following training (4-8 REMr). Both groups of REM-restricted rats eventually reached the same overall performance level as did nonrestricted controls, but 0-4 REMr animals were delayed in their improvement in the first few days and lagged behind controls in the middle portion of the training period. More importantly, performance gains of 0-4 REMr rats depended more on simple local cues throughout the 15-d study since, unlike control and 4-8 REMr animals, their error rate increased after daily disruption of the relationship between local (intramaze) cues and the food reward. Thus, although overall performance was only subtly and transiently impaired, due to the ability to use alternate, nonspatial behavioral strategies, complex associative (spatial) learning was persistently impaired by restricting REM for a short critical period each day.

Animals↗

PubMed2004

Activity changes of the cat paraventricular hypothalamus during stressor exposure.

Dorso-medial paraventricular hypothalamus (PVH) activity was assessed by light scattering procedures in freely behaving cats during auditory stressor exposure. Acoustic noise (> 95dB) raised plasma ACTH concentrations, somatic muscle tonus, respiratory frequency and cardiac rates; PVH activity peaked 0.8s following stimulation, and then markedly declined below baseline to a trough at 9.7s. Hypothalamic responses were not uniformly distributed across the recorded PVH field. Activity changes emerged from subregions within the visualized area, and were widespread at the overall activity zenith and nadir. Isolated pixels appeared opposite in activity pattern to overall changes. We suggest that transient activity increases represent initial PVH neural stress responses, and that subsequent profound declines result from neural inhibitory feedback.

Acoustic Stimulation↗

PubMed2003

State-dependent columnar organization of dorsal hippocampal activity in the freely-behaving cat.

We examined reflected light images from the dorsal hippocampus in freely-behaving cats to assess the topographical organization of neural activity expressed during sleep-waking states. Reflectance patterns, organized as columns along the CA3-CA1 axis which appeared during rapid eye movement sleep (REM) and waking states, were compared to baseline periods collected during quiet sleep (QS). The columns were not static across states or behaviors within a state, but showed inversion in activation/inactivation patterns, and narrowed or widened over time. A correlation between state-dependence and reflectance patterns emerged, with transitions to active waking and REM most likely exhibiting enhanced columnar patterning, relative to QS. No columnar patterns appeared in overlying neocortical areas or in control media. The columnar patterns suggest a highly structured functional state-dependent organization in the dorsal hippocampus, as has been previously predicted by anatomical studies.

Animals↗

PubMed2002

A spatial memory task appropriate for electrophysiological recordings.

We developed a novel method for assessing spatial learning that is compatible with the requirements of electrophysiological recording of multiple single neurons. The behavioral task utilized a rectangular track with 8 reward boxes of which a subset contained available food (bait). Errors were scored whenever the rat investigated a non-baited box location (commission), failed to investigate a baited box location (omission), or hesitated in front of a non-baited box location (hesitation). Several controls encouraged the animal to solve the task through allocentric cues rather than through procedural strategies or simple local cue pairing. The learning curve for this task (3-5 d to criterion) was comparable to that of other spatial learning tasks when adequately motivated. The types of errors varied as the animal learned the task. Unlike other spatial learning tasks, the multi-box track allows many repeated samples of the same spatial coordinates within a short period of time to allow, for example, reliable determination of place fields while recording from hippocampal cells. Multiple trials per session also allow for high intensity training important for many learning assessments such as the timing and type of sleep involved in learning and memory.

Analysis of Variance↗