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PubMed1977

[Aversive and appetitive effects induced by mesencephalic and hypothalamic stimulation (author's transl)].

Approach and escape latencies induced by hypothalamic or central grey stimulation were measured in the rat by means of a shuttle-box technique. In order to compare the effects obtained at various brain sites, the maximal value of the escape latency/approach latency ratio was determined within a given range of stimulation intensities. The ratio was shown to have high values at sites located in the ventral part of the central grey (in or near the dorsal raphe nucleus) or in the lateral hypothalamus. It was equal to zero for most of the sites located in the dorsal part of the central grey, as the rate regularly interrupted the stimulation without initiating it again. Intermediate values were obtained at sites located in the medial hypothalamus and in the dorsal pontine tegmentum.

Animals↗
PubMed1980

Spatial sharpening by second-order trigeminal neurons in crotaline infrared system.

Neural responses in the nucleus of the lateral descending tract of the trigeminal nerve (LTTD) of the rattlesnake Crotalus viridis were recorded. Neurons in the LTTD respond phasically to infrared stimulation of the pit organ, in contrast to the tonic responses that have been reported for the primary afferents. The receptive field dimensions of LTTD neurons are smaller than those of the primary afferents; some LTTD neurons have inhibitory regions within their receptive fields. The smaller receptive fields of neurons in the LTTD, as well as the phasic responses of these cells, might be a result of this inhibition. This is an instance of spatial sharpening and possibly enhancement of responses to time-changing stimuli due to excitatory and inhibitory neural interactions in a primary trigeminal nucleus.

Afferent Pathways↗
PubMed1981

Morphological identification of brain stem neurones associated with predatory behaviour elicited by lateral hypothalamic electrical stimulation in the cat: a retrograde transport study using horseradish peroxidase subsequent to an electrolytic lesion.

The combination of electrical stimulation of the lateral hypothalamus to elicit predatory behaviour, an electrolytic lesion and a subsequent HRP injection was used to identify brain stem neurones whose axons were affected by such hypothalamic stimulation. In contrast, the injection of HRP into such hypothalamic sites, without a prior lesion, resulted in a significant reduction in the number of labelled neurones. This suggests that an important contribution, namely those neurones which give rise to fibres which pass through the stimulated region, is underestimated by the later procedure.

Animals↗
PubMed1982

Lateralized loss of biting attack-patterned reflexes following induction of contralateral sensory neglect in the cat: a possible role for the striatum in centrally elicited aggressive behaviour.

A syndrome of "contralateral sensory neglect' was induced by hypothalamic knife cuts in 6 of 10 cats in which quiet biting attack behaviour could be elicited by lateral hypothalamic stimulation. The contralateral sensory neglect in the 6 affected cats was accompanied by a loss on the "neglected' side of the body of the patterned reflexes which mediate positioning of the head to bite and the jaw-opening component of biting. As a result, when these cats were stimulated in the lateral hypothalamus, although they continued to approach and even make tactile contact with the rat, they generally failed to bite it. Analysis of the histological and behavioural data suggested that damage to the nigrostriatal and/or striato/pallidonigral fibre systems provided the likely basis for both the induction of the contralateral sensory neglect and the lateralized patterned reflex loss. It was suggested, with respect to these specific patterned reflex components of the attack, that an important contribution may be made by the striatum.

Animals↗
PubMed1982

Late post-learning participation of entorhinal cortex in memory processes.

Mice of the BALB/c strain were bilaterally implanted with electrodes in the lateral entorhinal cortex (EC) in order to study the influence of post-trial EC stimulation on memory. The learning task was a food reinforced operant conditioning. At one of several time intervals after a first learning session, the experimental groups were stimulated for 80 s with subseizure current intensity. Testing was carried out 24 h later. In the first experiment, a continuous reinforcement schedule was used. EC stimulation had no effect when applied at the 30-s or 3-h intervals, but surprisingly a 30-min delayed stimulation greatly improved retention compared to performance of non-stimulated animals. In the second experiment, the same paradigm was used in a discriminative operant conditioning task. The same facilitation on retention was observed only with the 30-min delayed stimulation. Compared to previous data with hippocampal or hypothalamic stimulation, the present results reveal that EC is lately involved in memory processes.

Animals↗
PubMed1984

Electrical activity of the reticular formation during aversive and appetitive conditioning in rats.

Evoked potentials (EP) to a conditioned stimulus (CS) were recorded from several parts of the reticular formation (RF), the midbrain central gray (CG), the occipital cortex (OC), the basolateral amygdala and the ventrobasal thalamus during appetitive and aversive classical conditionings in rats. In addition, single unit activity to rewarding CS (+) and punishing CS (-) in a single discriminative classical conditioning was recorded from RF, OC, CG and the tectum. In the EP study, peak-to-peak (p-p) amplitudes, especially of the pontine RF, increased in the initial phase of pre-conditioning, in aversive conditioning and in appetitive conditioning but not in aversive pseudo-conditioning. The p-p amplitude in the pontine RF might reflect an amount of stimulus value the animal received. Slow negative potentials after CS presentation in RF was a reflection of body movements, indicating heavy involvement of RF in motor functions. In the single unit studies, cells which selectively responded to the CS (-) were more frequently found in the medial tegmental area close to the median raphe nucleus as compared to other areas. These results were considered to indicate high sensitivity of RF to the significance of the stimulus, and also the involvement of the medial tegmental area close to the median raphe nucleus in aversive emotional processes. Although many studies employing stimulation or lesion techniques have reported the steady relation between aversive emotional responses and CG, no supporting result was obtained in the present experiments.

Affect↗
PubMed1984

Effects of rewarding hypothalamic stimulation on plasma catecholamine levels in rats.

Plasma catecholamines were measured before, during and after exposure to lick-contingent rewarding hypothalamic stimulation, clock-triggered neutral hypothalamic stimulation, and licking maintained by water. Rewarding hypothalamic stimulation elicited a marked rise in plasma epinephrine levels which returned to baseline levels 3 min after the self-stimulation session. No changes in plasma epinephrine were observed under the latter two conditions. Increases in norepinephrine levels were more variable and seemed to correspond to motor activity being similar in the licking groups but unchanged with clock-triggered stimulation. These results indicate that stimulation of reward pathways may selectively influence adreno-medullary secretion.

Animals↗
PubMed1986

Single unit activity of locus coeruleus neurons in the freely moving cat. II. Conditioning and pharmacologic studies.

A series of experiments were carried out in which the single unit activity of presumed noradrenergic (NE) neurons in the area of the locus coeruleus (LC) was examined in freely moving cats during two conditioning paradigms and in response to pharmacologic manipulations relevant to anxiety. LC unit activity was examined during conditioned emotional response (CER) and conditioned food reward (CFR) training. During CER training, LC units showed a large increase in activity in response to a stimulus paired with a noxious air puff, whereas no increase in unit activity was seen in response to a stimulus not paired with the air puff (both comparisons relative to their appropriate control conditions). By contrast, during CFR training, a stimulus paired with a rewarding food delivery did not elicit a significant increase in LC unit activity relative to its appropriate control condition. Therefore, NE units in the LC greatly increase their activity in response to a stimulus that predicts the occurrence of a noxious event, but not in response to a stimulus that predicts the occurrence of a rewarding event. Administration of the anxiolytic drug diazepam (0.25 and 2.0 mg/kg, i.p.) had no significant effect on the spontaneous activity of LC neurons, but significantly reduced the excitatory response of LC neurons to simple stimuli. Administration of the anxiogenic drug yohimbine (2.0 mg/kg, i.p.) significantly increased the spontaneous activity of LC neurons. These results support the hypothesis that LC neurons play a role in aversive but not appetitive conditioning, and are consistent with the hypothesis that these neurons may play a role in anxiety. These data are discussed within the broader context of LC neurons mediating the organism's adaptive response to environmental or physiological challenges.

Acoustic Stimulation↗
PubMed1987

Motivational properties of opioids: evidence that an activation of delta-receptors mediates reinforcement processes.

The role of central delta-opioid receptors in the mediation of opioid reinforcement and endogenous reward processes was examined using a non-biased place-preference conditioning procedure. Intracerebroventricular (i.c.v.) administration of the selective delta-receptor agonist, [D-Pen2, D-Pen5]-enkephalin (DPDPE, 10.0-25.0 micrograms) produced a significant preference for the drug-associated place and a similar effect was observed following i.c.v. injections of morphine (10.0 micrograms). Administration of the delta-receptor antagonist, ICI 174,864, at doses (1.0-5.0 micrograms, i.c.v.) which had no aversive effects when tested alone, abolished the reinforcing properties of DPDPE. Such treatment did not, however, modify the effect of morphine. These findings demonstrate the involvement delta- as well as mu-receptors in the motivational properties of opioids and suggest that the activation of either receptor type is sufficient for the elicitation of appetitively reinforcing effects.

Animals↗
PubMed1993

Morphine-induced place preference in the CXBK mouse: characteristics of mu opioid receptor subtypes.

The role of mu opioid receptor subtypes, mu 1 and mu 2, in morphine-conditioned place preference was examined using ddY and mu 1 opioid receptor-deficient CXBK mice. In ddY mice, the mu receptor agonist morphine caused a dose-related preference for the drug-associated place, but the kappa agonist U-50,488H produced a dose-related place aversion. These results demonstrated that the mouse is available for place preference conditioning using opioids. Under this condition, the influence of pretreatment with the selective mu 1 opioid receptor antagonist naloxonazine on morphine-induced place preference was investigated in ddY mice. Although pretreatment with the selective mu 1 antagonist naloxonazine (35 mg/kg, s.c.) did not modify the morphine-induced place preference, pretreatment with the selective mu antagonist beta-funaltrexamine (beta-FNA 10 mg/kg, s.c.) eliminated the appetitive effect of morphine. Furthermore, morphine (1-5 mg/kg, s.c.) produced a dose-related preference for the drug-associated place in CXBK mice. These findings suggest that the morphine-induced conditioned place preference may be mediated by naloxonazine-insensitive sites (mu 2 opioid receptors). In addition, chronic infusion of the dopamine D1 antagonist SCH23390 (1.0 mg/kg/day) during the conditioning sessions eliminated the morphine-induced place preference in CXBK mice. Similarly, morphine combined with naloxonazine failed to produce the place preference in ddY mice chronically treated with SCH23390. The blocking effect of SCH23390 on the morphine-conditioned place preference suggests that mu 2 receptors may regulate the dopaminergic system, especially dopamine D1 receptors, and are also involved in the reinforcing effects of morphine.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1990

Representation of time.

Memory representation for time was studied in two settings. First, an analysis of timing in a laboratory analog of a foraging situation revealed that departure times from a patchy resource followed a Weber Law-like property implied by scalar timing. A trial-by-trial analysis was then pursued in a similar but more structured experimental paradigm, the Peak procedure. Study of covariance structures in the data implicated scalar variance in the memory for time as well as in the decision process, but the correlation pattern ruled out multiple access to memory within a trial.

Animals↗
PubMed1990

Alternative representations of time, number, and rate.

Three facts of time perception are described based upon a temporal generalization task for rats (the peak procedure) in which food reinforcement is delivered on half the trials following the first lever-press response after some fixed interval after signal onset. (1) The mean response rate as a function of time is a smooth, slightly asymmetric, function with a maximum near the time of reinforcement; (2) the response rate on individual trials is characterized by an abrupt change from a state of low responding to a state of high responding and finally another state of low responding (break-run-break pattern); and (3) the mean response rate in 12-s and 20-s peak procedures is similar when plotted against time relative to the time of reinforcement (superposition). An information-processing version of scalar timing theory is described and compared to an alternative connectionist version of scalar timing theory that involves multiple oscillators and an autoassociation network. Psychological, mathematical and biological descriptions of the two versions are described and some possible extensions of the connectionist version are proposed to deal with perception of number, rate, and spatial orientation.

Animals↗
PubMed1990

Honey bee cognition.

The visual memory of honey bees is stored pictorially. Bees will accept a mirror-image reversal of a familiar pattern in the absence of the original, but prefer the original over the reversal; the matching system of bees, therefore, does not incorporate a mirror-image ambiguity. Bees will not accept a rotation of a familiar vertical pattern, but readily recognize any rotation of a horizontal pattern; the context-specific ability to make a mental transformation seems justified by natural contingencies. Bees are able to construct and use cognitive maps of their home area, though it is possible to create conditions under which they lack useful cues. Other experiments suggest that recruits, having attended a dance in the hive specifying the distance and direction of a food source, can evaluate the "plausibility" of the location without leaving the hive; this suggests a kind of imagination.

Animals↗
PubMed1981

Hippocampal slow wave activity during appetitive and aversive conditioning in the cat.

The electrical activity of the dorsal and ventral divisions of the hippocampus was investigated quantitatively during the development of discriminative operant training and defensive conditioning. Signal-related (respondent, sign-tracking) and goal-directed (operant, 'voluntary') activities and their hippocampal electrical correlates were compared. Signal-related behaviour was accompanied by significantly higher frequency spectral peaks than lever press behaviour. Spectral peaks were higher during lever pressing in early stages of training as compared to criterion performance. In defensive conditioning overt sign-tracking behaviour disappeared but spectral peak shifts toward higher values upon signal presentation persisted. Comparison of dorsal and ventral hippocampal activity revealed high coherence values and similar frequency shifts during behaviour transitions. These findings argue against suggestions that a close relationship exists between elementary motor acts and hippocampal EEG.

Animals↗