Biomedical subjects

J M Edeline

Publications and source records attributed to J M Edeline.

28 records · Page 2Linked to original sources

PubMed1992

Associative retuning in the thalamic source of input to the amygdala and auditory cortex: receptive field plasticity in the medial division of the medial geniculate body.

The medial division of the medial geniculate body (MGm) projects to the lateral amygdala and the upper layer of auditory cortex and develops physiological plasticity rapidly during classical conditioning. The effects of learning on frequency receptive fields (RFs) in the MGm of the guinea pig have been determined. Classical conditioning (tone-footshock), as indexed by rapid development of conditioned bradycardia, produced conditioned stimulus (CS)-frequency specific RF plasticity: increased response at the CS frequency with decreased responses at other frequencies, both immediately and after a 1-hr retention period. Sensitization training produced only general changes in RFs. These findings are considered with reference to both the elicitation of amygdala-mediated, fear-conditioned responses and the mechanism of retrieval of information stored in the auditory cortex during acquisition.

Amygdala↗

PubMed1992

Stimulation at a site of auditory-somatosensory convergence in the medial geniculate nucleus is an effective unconditioned stimulus for fear conditioning.

The medial division of the medial geniculate nucleus (MGm) and the posterior intralaminar nucleus (PIN) are necessary for fear conditioning to an auditory conditioned stimulus (CS), receive both auditory and somatosensory input, and project to the amygdala, which is involved in production of fear conditioned responses. If CS-unconditioned stimulus (US) convergence in the MGm-PIN is critical for fear conditioning, then microstimulation of this area should serve as an effective US during classical conditioning, in place of standard footshock. Guinea pigs underwent conditioning (40-60 trials) using a tone as the CS and medial geniculate complex microstimulation as the US. Conditioned bradycardia developed when the US electrodes were in the PIN. However, microstimulation was not an effective US for conditioning in other parts of the medial geniculate or for sensitization training in the PIN or elsewhere. Learning curves were similar to those found previously for footshock US. Thus, the PIN can be a locus of functional CS-US convergence for previously for footshock US. Thus, the PIN can be a locus of functional CS-US convergence for fear conditioning to acoustic stimuli.

Amygdala↗

PubMed1991

Subcortical adaptive filtering in the auditory system: associative receptive field plasticity in the dorsal medial geniculate body.

Highly specific subcortical receptive field (RF) plasticity was found in the dorsal division of the guinea pig medial geniculate body during cardiac conditioning to a tonal frequency. There was increased response to the conditioned-stimulus (CS) frequency, and there were decreased responses to adjacent frequencies, especially at the pretraining best frequency (BF), which often resulted in a shift of tuning such that the CS became the new BF. Moreover, 1 hr later the effects were stronger, more sharply tuned, and centered on the CS frequency. A sensitization paradigm produced only broad, general increases of response across the RF. These findings reveal that the analysis of sensory RF dynamics is a valuable approach to understanding the neural mechanisms of information processing in learning and memory.

Animals↗

PubMed1991

Conditioned hippocampal cellular response to a behaviorally silent conditioned stimulus.

Multiunit activity (MUA) was chronically recorded in the hippocampal CA3 field of rats using a blocking paradigm with conditioned suppression of lever pressing for food as the measure of conditioning. In Experiment 1, a classical blocking paradigm demonstrated the good conditionability of 2 stimuli (a light and a tone) and their respective ability to block each other. In Experiment 2, MUA was recorded in CA3 cells in rats submitted to a similar paradigm. Four groups received either tone (groups B and B1) or click (groups BC and B1C) conditioned stimulus (CS) presentations that were followed immediately by an electrical footshock (unconditioned stimulus, US). The rats were then given either 40 (groups B and BC) or 1 (groups B1 and B1C) tone + light-footshock presentations. During test sessions, the animals showed MUA responses to the added CS (light), with no conditioned suppression of lever presses occurring during CS presentations. The results of Experiment 3 strongly suggest that hippocampal increase in cellular activity to the light appeared at the first compound trial presentation. Conditioning to the light obtained by increasing the US intensity after the single compound trial suggests that the hippocampal response reflects a redundant CS-US association (light-shock). Long-term retention tests given 45 days after the end of conditioning revealed that behavioral and hippocampal responses could still be detected but only in response to the stimulus that had elicited a behavioral response during learning.

Animals↗

PubMed1991

Thalamic short-term plasticity in the auditory system: associative returning of receptive fields in the ventral medial geniculate body.

The effects of classical conditioning on frequency receptive fields (RFs) in the ventral, tonotopic part of the guinea pig (Cavia porcellus) medial geniculate ventral body (MGv) during cardiac conditioning to a single tone frequency were studied. Associative frequency-specific plasticity, in which the RF was returned to the frequency of the conditioned stimulus (CS), developed if the CS frequency was within 0.125 octave of the pretraining best frequency. Otherwise, a general increase across the RF developed. Sensitization training also produced general increased responses. The frequency-specific plasticity was short-term and observed only immediately after training, whereas the general effects were maintained. These results suggest that frequency-specific RF plasticity in the MGv may be a substrate of short-term mnemonic processes that could participate in long-term storage of information and modification of the representation of the CS at the auditory cortex.

Animals↗

PubMed1990

Frequency-specific plasticity of single unit discharges in the rat medial geniculate body.

The effects of conditioning (tone-footshock pairing) on single unit discharges in the magnocellular medial geniculate (mMG) were examined in rats submitted to pairing under ketamine. For all the semichronic animals, the conditioned suppression of lever pressing for food observed subsequently indicated that at the behavioral level, an acquisition takes place during the pairing. The activity of 37 single unit activities was recorded both during pairing and during determination of frequency-selectivity before and after pairing. The results showed that 54% (20/37) of the cells exhibited plasticity of their evoked response (increase or decrease) during pairing compared with the habituation or the sensitization phase. Moreover, 75% of these changes (15/20 cells) were specific for the frequency used as conditioned stimulus during conditioning. Modifications of background activity were observed during pairing or sensitization and were never correlated with modifications of the evoked responses. These results suggest that specific modifications of the frequency receptive field of the mMG cells occur during acquisition of classical conditioning.

Acoustic Stimulation↗

PubMed1990

Discriminative long-term retention of rapidly induced multiunit changes in the hippocampus, medial geniculate and auditory cortex.

Multiunit activity was chronically recorded in the hippocampus (CA3 field), the magnocellular medial geniculate (MGm) and the auditory cortex (AC) of rats during acquisition (12 daily sessions, 10 trials per session) and long-term retention of differential classical conditioning (tones paired with footshocks). Marked increases of multiunit discharges to CS + presentations were first detected in the MGm (5-10 trials) followed (10-20 trials) by the emergence of discriminative responses in the hippocampus and in the AC. During long-term retention tests, 45 days after the end of conditioning, CS + selective responses were observed in the 3 structures. We propose that learning-induced changes in the conditioned stimulus (CS) sensory pathway can have the same temporal stability as the sensory plasticity observed during development or post injury in adult animals.

Animals↗

PubMed1988

Retention of CS-US association learned under ketamine anesthesia.

In order to assess learning possibilities under ketamine anesthesia, rats underwent a pavlovian conditioning (tone paired with foot-shock), and were subsequently tested in a conditioned suppression of lever pressing for food paradigm. First, two sessions of 70 trials were conducted, on 4 groups of anesthetized rats: a conditioned group (group C) experienced the tone (CS+) always paired with foot-shocks, whereas a discriminative group (group D) was submitted to a differential conditioning (CS+ followed by the US and a CS- always presented alone). Another group (habituated, H) received presentations of tone (CS+) alone and the fourth group (naive animals, N) was never anesthetized. Seven days later, while rats were pressing the lever to get food, CS+ presentations elicited a significant conditioned suppression of instrumental responses only in groups C and D. Moreover, a differential effect between CS+ and CS- was obtained for group D. These results indicate that a Pavlovian conditioning can occur under anesthesia, and then that its memory can last at least 7 days. The particular specific effects of ketamine are discussed to account for these results.

Anesthesia, General↗

PubMed1988

Multiunit changes in hippocampus and medial geniculate body in free-behaving rats during acquisition and retention of a conditioned response to a tone.

Multiunit activity (MUA) was recorded chronically in the hippocampus (CA3) and the medial geniculate body (mMG) during habituation to a tone followed by conditioning (tone paired with footshock) or pseudoconditioning (tone/footshock unpaired) in rats previously trained in a lever-pressing for food task (VI 60). In the conditioned group pairing tones with footshocks rapidly induced an increase in the initial CS-evoked response in the mMG, followed by the emergence of a hippocampal response and a marked conditioned suppression of lever-pressing to the tone. In contrast, in the pseudoconditioned group, the stimulus induced only transient cellular changes in the hippocampus and in the mMG, while no behavioral suppression to the tone could be seen. Moreover, presentations of the CS 45 days later induced multiunit and behavioral responses in both structures, only in the conditioned group. These results are used for discussion of the role of learning-induced changes in the sensory structure (mMG) as compared with changes in an associative structure (hippocampus), during acquisition and retention of a conditioned response.

Acoustic Stimulation↗

PubMed1987

Hippocampal associative cellular responses: dissociation with behavioral responses revealed by a transfer-of-control technique.

Multiunit activity was recorded in the CA3 field of the dorsal hippocampus in freely moving rats during classical conditioning and subsequent presentation of the CS on operant baselines for food reward as well as shock avoidance. Rats were first trained in a nonsignaled bar-pressing-dependent shock omission task and in a food-motivated lever-pressing task (60-s VI). Five sessions with presentations of a previously habituated tone as a CS paired with footshock as a US were then given. Testing was carried out by presenting the CS alone while behavioral responses were maintained by reinforcement in both instrumental tasks on alternate sessions. As expected, the CS induced a marked suppression of lever pressing for food reward and a marked enhancement of bar-pressing for shock avoidance. The analysis of the frequency of multiunit discharges to the CS revealed that the hippocampal cellular responses established during classical conditioning were maintained while two different behavioral responses were exhibited to the CS. The results showed that the associative response of hippocampal neurons may be dissociated from the Pavlovian conditioned responses the CS elicits. They support the hypothesis that hippocampal cellular responses represent a neural index of the acquired CS-US associative representation.

Animals↗