EFFECTS OF ELECTRIC STIMULATION OF BRAIN-STEM RETICULAR-FORMATION ON HIPPOCAMPAL THETA RHYTHM AND MUSCLE ACTIVITY IN UNANESTHETIZED, CERVICAL-TRANSECTED AND MIDBRAIN-TRANSECTED RATS | Academic Article individual record
abstract

This study tested certain theories on the significance of hippocampal theta rhythm, as it relates to the descending motor functions of various levels of the brain stem reticular formation (BSRF). Electric stimulation of 100 sites of 10 unanesthetized, cervical-transected rats revealed that stimulation of either midbrain, pontine, or medullary BSRF simultaneously evoked hippocampal theta rhythm and increased EMG activity in vibrissae and neck muscles. Stimulation of 12 sites in 5 rats caused a brief 'rebound' EEG activation during which theta frequency increased over that during the stimulation; stimulation of 10 sites in 4 rats caused a rebound increase in EMG activity. Comparison of pulse duration effects (300/sec stimulation) showed that optimal activating responses occurred with 0.3 msec pulses, with no effect at durations longer than 1 msec. Comparison of frequency effects (0.3 msec pulses) showed that simultaneous EEG and EMG activations occurred at all frequencies tested between 100 and 300/sec. With higher frequency stimulation of 7 BSRF sites in 5 rats, hippocampal theta rhythm increased 1-4 waves/sec, and at 9 other sites in 5 rats, EMG response intensity increased progressively with slower stimulation frequencies. When the rats were paralyzed with curare, and their EMG activations blocked, EEG activations could still be elicited. In a given rat, curare decreased the frequency of stimulus-evoked theta by 0.5-2 waves/sec. Increasing stimulus voltage at 6 of the 16 BSRF sites tested in curarized rats increased theta frequency by 0.5-1.5 waves/sec, or converted it into low voltage, fast activity. Stimulation of 79 BSRF sites in 7 midbrain-transected rats consistently activated neck muscles, as well as one or more contralateral or ipsilateral forelimb muscles. Twenty-six patterns of forelimb muscle activation were observed, involving different degrees of contraction intensity in either or both flexor or extensor muscles on the same limb. Increasing the stimulus voltage in a given BSRF area increased the number of muscles responding and the intensity of their response. © 1974.

author list (cited authors)
KLEMM, W. R.
publication date
1972
publisher
Elsevier bv Publisher
published in
Brain Res Journal
keywords
  • Hippocampus
  • Rats
  • Reticular Formation
  • Electroencephalography
  • Motor Neurons
  • Animals
  • Electric Stimulation
  • Mesencephalon
  • Cordotomy
  • Spinal Cord
  • Electromyography
  • Brain Stem
citation count

53