Path neuron system of medial forebrain bundle as a possible substrate for hypothalamic self-stimulation

Research output: Contribution to journalArticle

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Abstract

Long descending fibers of the medial forebrain bundle terminate on path neurons in the lateral hypothalamic and preoptic regions. The axons of the path neurons bifurcate to project rostrally and caudally giving off many short collaterals to adjacent path neurons. Thus, the path neuron system of the medial forebrain bundle forms a series of reverberatory loops in the lateral hypothalamus. findings obtained by combining conditioning test stimulation and instrumental self-stimulation techniques in the rat indicate that (a) such neurons, which, like path neurons, give short excitatory collaterals to each other, are excited by lateral hypothalamic rewarding electrical pulses. Weak stimulation of the lateral hypothalamic self-stimulation loci results in poststimulatory excitability changes time course of which resembles the shape of excitatory postsynaptic potentials. The 0.5-0.6 msec long latencies correspond to the sum of the synaptic transmission time plus a few tenths of a msec required for the conduction of excitation in the collaterals between adjacent path neurons and for the electrotonic conduction of depolarization in the postsynaptic (i.e. synaptically activated) path neurons (Experiments 1 and 2). (b) Excitability curves obtained with more intense stimulation reflect definite signs of repeated synaptic activation (Experiment 1) and reverberation (Experiment 3). Rebound aftereffects recorded immediately after the end of rewarding intracranial stimulus trains also suggest that, during stimulation, reverberatory circuits are activated. However, a negative feedback inhibition which is also reflected by the excitability curves (Experiment 3) suppresses the reverberatory activity until the end of the rewarding stimulus train and a release occurs afterwards. The observations are interpreted as indicating that the excitation of the path neuron system of medial forebrain bundle is responsible for the lateral hypothalamic self-stimulation. With regard to the various psychological theories of reinforcement (the expectancy model and motor facilitation hypothesis of Milner, Miller's go mechanism, the postinhibitory rebound theory of Grastyán, drive-reduction and drive-induction theories) a possibility is also discussed that the path neuron system is capable to serve as an unitary anatomical substrate for reward.

Original languageEnglish
Pages (from-to)315-328
Number of pages14
JournalPhysiology and Behavior
Volume10
Issue number2
DOIs
Publication statusPublished - 1973

Fingerprint

Medial Forebrain Bundle
Self Stimulation
Neurons
Lateral Hypothalamic Area
Psychological Theory
Excitatory Postsynaptic Potentials
Reward
Synaptic Transmission
Axons

Keywords

  • Anatomy of Reward
  • Lateral hypothalamus
  • Medial forebrain bundle
  • Positive feedback
  • Rebound excitement
  • Refractory periods of rewarding structures
  • Reverberation
  • Self-stimulation
  • Synaptic activation
  • Theories of reinforcement

ASJC Scopus subject areas

  • Physiology (medical)
  • Behavioral Neuroscience

Cite this

Path neuron system of medial forebrain bundle as a possible substrate for hypothalamic self-stimulation. / Szabó, I.

In: Physiology and Behavior, Vol. 10, No. 2, 1973, p. 315-328.

Research output: Contribution to journalArticle

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