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HANDBOOK (JF Pin'SIOLOGV' ^ NEUROPHYSIOLOOI' II 



clectrocorticographic responses are in all points simi- 

 lar, if not identical, with the 'arousal response' as 

 elicited by stimulation of the brain-stem reticular for- 

 mation (59). Furthermore the amygdaloid 'arousal" 

 pattern with activation of the fast spindles (see p. 1 403 ) 

 can be elicited in one anngdala by stimulating the 

 contralateral amygdala. These observations suggest a 

 close relationship of the amygdaloid complex with 

 subcortical regions exerting diffuse regulatory effects 

 upon the electrical activity of the cortex. 



Effects upon Spoiilariiutts or Evoked Soniiildinohn Activities 



Spontaneous mo\ements going on at the time of 

 onset of amygdaloid stimulation are usually arrested 

 therein-. Thus in anesthetized preparations shivering, 

 struggling and spontaneous chloralose-jerks are in- 

 hibited and there is concomitant reduction in muscle 

 tone (133, 135). In unanesthetized animals this 

 'arrest' reaction assumes the form of a sudden cessa- 

 tion of motor activities in which the animal is engaged 

 at the time of onset of stimulation. In the awake 

 animal there is usually no decrease but an increase in 

 muscle tone when this 'arrest' reaction occurs (72, 

 133, 172, 190, 245). 



Spinal reflexes and cortically evoked movements 

 are facilitated or inhibited (fig. 5.-1) by amygdaloid 

 stimulation (133). Points producing facilitation and 

 those eliciting inhibition are not clearly separated but 

 overlap extensively. 



Motor Responses 



In awake freely moving animals a variety of tonic 

 movements can be elicited by stimulation of the 

 amygdala. The most frequent response is contraver- 

 sive turning of the head and eyes, sometimes together 

 with rotation inducing a posture as if the animal were 

 looking backward over its shoulder. More rarely, 

 vertical head movements are seen. If stimulation is 

 maintained, the animal may be induced to circle 

 around or to roll over on its side (11, 13, 22, 73, 87, 

 88, 133, 135, 155. 175. 190, 245). 



Sometimes postural movements of the extremities 

 are elicited. They usually invoke flexion of the con- 

 tralateral and extension of the ipsilateral limbs (135). 

 Similar tonic movements are also observed in man 

 (61, 129). 



Clonic rhythmic movements are sometimes induced 

 by amygdaloid stimulation. Most often these involve 



the ipsilateral face" (11, 13, 22, 23, 72, 73, 87, 152, 

 172, 175, 190, 239, 245); more rarely, the extremities 



(87> -S.^))- 



Complex rhvthmic movements related to eating, 

 such as licking, chewing and swallowing, are fre- 

 quently obserxed upon amygdaloid stimulation. Often 

 a latent period of 5 to 20 sec. elapses between the onset 

 of stimulation and their appearance (11, 13, 22, 72, 

 73, 87, 88, 129, 133, 135, 172, 175, 186, 190, 209, 

 239, 245). In .some instances these 'masticatory' move- 

 ments assume a different character and the animal 

 acts as if trying to disgorge a foreign body or something 

 distasteful. This often leads to gagging and retchina;, 

 but seldom to true \()UHtins; (72, 73, 87, 172, 190, 



-'45)- 



Rarely, vocalization occurs upon stimulation of the 

 amysdala (72, 168, 172, 190, 245). 



[ 'egetdlive Responses 



Respiratory changes are very frequently elicited by 

 amygdaloid stimulation. These may affect all physical 

 characteristics of respiration, such as rhythm, ampli- 

 tude and rest position of the thorax (72). The most 

 frequent response is inhibition of respiration (fig. 5.-1) 

 affecting both rhythm and amplitude (11, 12, 72, 88, 

 133, 135, 160, 172, 201, 245). Often there is respira- 

 tory arrest with escape 25 to 60 .sec. later. Acceleration 

 of respiration (fig. ^fi), with increased or decreased 

 amplitude, often preceded by a short period of 

 apnea, is less frequently seen (12, 72, 88, 146, 147, 

 172, 190). Specific modifications of respiration, such 

 as sniffing, sneezing and coughing, are also sometimes 

 produced (72, 88, 133, 155, 175, 190). 



\'arious cardiovascular responses occur upon amyg- 

 daloid stimulation (11, 12, 22, 41, 72, 88, 149, 168, 

 172, 188, I go, 201). Both increase and decrease in 

 arterial pressure and more rarelv, acceleration or 

 slowing of the heart beat can be produced. Chans;es 

 in heart rate do not show anv consistent relationship 

 with the direction of the arterial pressure response 

 (12). 



Gastrointestinal motility and secretion can be in- 

 hibited (fig. 5/)) or activated by amygdaloid stimula- 

 tion (11, 15, 56, 149, 150). Defecation (fig. 6) and 

 even more frequently micturition may l)e induced, 



■' Since these movements often appear only after some latent 

 period, do not follow the frequency of the applied electrical 

 stimuli, may outlast the end of the stimulation and cannot be 

 reproduced by stimulation of adjacent parts of the brain or the 

 dura covering the middle fossa, they cannot be attributed to 

 spread of current to the facial nerve. 



