CHAPTER XXX 



Central mechanisms of vision 



S. HOWARD BARTLEY | Department of Psychology, Michigan State University, East Lansing, Michigan 



CHAPTER G O N T E N I S 



Types of Data 



Commonality in Modes of Study 

 Phenomena of Vision 

 Phenomena of the Optic Pathway 



Brain waves; spontaneous and evoked 



Optic pathway 



Cortical response 



Activation of cortex by stimulation of radiation 



Activity in regions other than optic cortex 



Cortical localization 



Properties of dendrites 

 Visual Phenomena to be Explained 



Gross Response to Gross Intensity Relations 



Area of Target 



Brightness 



Flicker and Fusion 



Brightness Enhancement 



Bilateral Functions 



Brightness Contrast 



Visual Movement 



Color Vision 



THE PRESENT CHAPTER, devotcd to Central mechanisms 

 of vision, must deal with two diverse sets of phe- 

 nomena. One set comprises the phenomena that, 

 taken together, we call vision. The other is the group 

 of neurophysiological phenomena that constitute the 

 activities of the central end of the optic pathway. The 

 visual phenomena must be considered first, for they 

 are the items to be accounted for, if possible, by what 

 we know about the optic pathway and its associated 

 systems. 



Vision is the behavior of the organism that stems 

 more or less directly from optic pathway activity. 

 Vision includes both the introspective (the experien- 

 tial) and the motor. Visual behavior in question is 



divisible in still another way. Part of it is the immedi- 

 ate discriminatory reaction which we call visual per- 

 ception. Perception is not only experiential but also 

 motor in expression. Another part of behavior is in 

 the form of imagery, etc., that is, a function of the 

 visual mechanism when the eye is not stimulated. 



Material appropriate in the discussion of central 

 visual mechanisms stems first from what we know 

 about visual phenomena in accord with the definition 

 of vision just given and from what we have found out 

 from direct investigation of the activity of the entire 

 optic pathway. We may also legitimately include cer- 

 tain inferences that seem to be necessary to bridge the 

 gaps in our knowledge and to provide a basis for 

 further investigation. 



TYPES OF D.«iTA 



In this portion of the chapter we must specify, at 

 least in general, the kinds of phenomena with which 

 we shall deal. They are of two kinds so diverse that 

 they generally are dealt with in entirely separate dis- 

 courses. The one class is visual and includes the ex- 

 periential outcomes of the action of the optic pathway 

 activated by photic radiation. The other class of 

 phenomena is neurophysiological. The task of the 

 present chapter seeins to be one of relating the two 

 classes of phenomena. 



Commonality in Modes of Study 



The fundamental requirement in relating vision to 

 the various phenomena in the optic pathway is for 

 the two sets of events to be initiated by the same ex- 

 ternal event (stimulus). In this way, one can .say that 



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