1932] Poliak: Afferent Fiber Systems, Primate Cerelral Cortex 99 



be insufficient to produce a definite sensation (in the present instance 

 that of an octave), but will nevertheless suffice to create a certain 

 functional correlation. When, therefore, at another time, two such 

 correlated groups of hair cells are stimulated by two different stimuli, 

 for instance A^ and Ai, the previously created functional correlation 

 will appear in subjective interpretation in the form of a "similarity" 

 or a "resemblance" of these two stimuli. If on the contrary, two 

 groups of hair cells which do not stand in connection by spironeural 

 fibers are stimulated by two different simple stimuli (for instance A^ 

 and J-ii, or A^ and Am, and so forth), no similarity in sensation will 

 be evoked. It is pure supposition that the relation of an orthoneural 

 and a spironeural group of neurons might amount to exactly one 

 octave. Yet if this is proved by future investigations as true, the 

 * ' similarity of octaves ' ' will find its morphological explanation. (It is, 

 however, possible that other relations co-exist with a smaller or a 

 greater interval.) In this case the appearance of other phenomena 

 called consonance (accords, harmonies) would be understood. A per- 

 fect consonance would exist between A^ and Ai ; a pleasant impression 

 would also exist between A^ and Am, A-^ and Aiv, A^ and Ay, A^ and 

 A VI since the distinction in perception must increase here (no uncer- 

 tainty or indefiniteness as, for example, in relation of A^ and An, the 

 latter being close to Ai ; or between A^ and Avu). The phenomenon of 

 dissonance can also be explained by the present hypothesis. A^ is 

 "dissonant" to A, (by reason of the immediate neighborhood). Since 

 An stands in a "consonant" relation with An, a similar "dissonant" 

 effect will be produced if A^ and An are stimulated simultaneously. 

 The same explanation must be applied in respect to A^ and Avu since 

 Avii is in a "consonant" relation to A^, which in turn, is in a "dis- 

 sonant" relation to A^. The subjective interpretation of the quality 

 of similarity, of the degree of consonance or dissonance of any two 

 tones will, therefore, depend on the interval or distance of two or more 

 stimulated groups of hair cells from one another and on their spiro- 

 neural connections; closely neighboring groups, when their ortho- 

 neural dendrites do not overlap, produce a sensation of two different 

 tones, not pleasant when heard together, and equally so, if two groups 

 of hair cells are stimulated which are close to the group which is by 

 means of spiral fibers in the relation of an octave to one of the stimu- 

 lated groups. Since for every group of hair ceUs throughout the 

 cochlea there is another group which is in the relation of an octave to 

 it — as many groups as there are octaves (A^ to Ai, Ai to A^ in circle. 



