Neural Mechanisms of Decision Making 275 



these situations reflects the coding and processing of information 

 as the brain performs differentiated conditioned responses to two 

 intermittent photic stimuh differing in frequency; and 2) the 

 estabhshment and performance of such differentiated behaviors 

 involve the measurement of similarity between past experience, 

 as reflected primarily in the neural activity of nonspecific regions 

 of the brain, and present stimulus configuration, as refiected 

 primarily by the specific sensory systems of the brain. 



The observations of "assimilation of the rhythm" which have 

 been reported by many workers suggest that the brain has the 

 capacity to reproduce previously experienced patterns of neural 

 activity. Manifestation of such endogenously generated patterns 

 is marked in nonspecific systems. During generalization, behavioral 

 performance seems to be accompanied by departures from stimulus- 

 bound response, notably in the cortex of the relevant sensory 

 modality and in the reticular formation. Computer analysis of 

 waveforms from various structures during such behavior shows 

 that these two regions cHsplay clear evidence of endogenously 

 generated coinponents appropriate to the behavior, while other 

 regions of the brain respond to the stimulus more accurately. 

 Analogous observations have been made when cfifferentially 

 trained animals commit errors. 



These data, which are compatible with the hypotheses, are 

 contradicted by the failure to elicit erroneous performance dif- 

 ferentially as a consequence of central stimulation at a frequency 

 discordant with the frequency of a concurrent peripheral con- 

 ditioned stimulus. It has, however, been demonstrated that 

 temporal patterns of excitation at a site can serve as coded infor- 

 mation for the brain. Evidence has also been presented indicating 

 that a crucial step in cortical data processing may take place at 

 the time when influences arrive from the nonspecific system. 



To date, therefore, we have not succeeded in establishing an 

 unequivocal functional role for labeled potentials as direct reflec- 

 tions of data processing in the brain. However, an increasing and 

 consistent body of evidence does seem to support the view that a 

 cortical-reticular interaction is an important component in the 

 evaluation of incoming information in the context of past ex- 

 perience. 



