Key Arguments

• Dreyfus reports that 'The latest suggestion from Jerome Lettvin of M.I.T. is that the diameter of the axon may play a crucial role in processing information by acting as a filter.'
• On Lettvin’s view, 'An individual neuron fires at a certain frequency. The diameter of its various axon branches would act as low pass filters at different cutoff frequencies. Output from a given cell would then produce different frequencies at different terminals.'
• Further, 'The filter characteristics of the axon would vary with its diameter which in turn might be a function of the recency of signals passing down that axon, or even, perhaps, of the activation of immediately environing axons.'
• Dreyfus infers that 'If such time factors and field interactions play a crucial role, there is no reason to hope that the information processing on the neurophysiological level can be described in a digital formalism or, indeed, in any formalism at all,' highlighting the continuous, context‑sensitive, and interactive nature of these processes.

Source Quotes

These incoming barrages are of a different value depending upon the pathway and a standing bias. Indeed, so much can be done by means of this graded and nonlinear local phenomenon prior to the initiation of any postsynaptic impulse that we can no more think of the typical synapse in integrative systems as being a digital device exclusively as was commonly assumed a few years ago, but rather as being a complex analog device. . . .5 The latest suggestion from Jerome Lettvin of M.I.T. is that the diameter of the axon may play a crucial role in processing information by acting as a filter.6 An individual neuron fires at a certain frequency. The diameter of its various axon branches would act as low pass filters at different cutoff frequencies.

These incoming barrages are of a different value depending upon the pathway and a standing bias. Indeed, so much can be done by means of this graded and nonlinear local phenomenon prior to the initiation of any postsynaptic impulse that we can no more think of the typical synapse in integrative systems as being a digital device exclusively as was commonly assumed a few years ago, but rather as being a complex analog device. . . .5 The latest suggestion from Jerome Lettvin of M.I.T. is that the diameter of the axon may play a crucial role in processing information by acting as a filter.6 An individual neuron fires at a certain frequency. The diameter of its various axon branches would act as low pass filters at different cutoff frequencies. Output from a given cell would then produce different frequencies at different terminals. The filter characteristics of the axon would vary with its diameter which in turn might be a function of the recency of signals passing down that axon, or even, perhaps, of the activation of immediately environing axons.

Output from a given cell would then produce different frequencies at different terminals. The filter characteristics of the axon would vary with its diameter which in turn might be a function of the recency of signals passing down that axon, or even, perhaps, of the activation of immediately environing axons. If such time factors and field interactions play a crucial role, there is no reason to hope that the information processing on the neurophysiological level can be described in a digital formalism or, indeed, in any formalism at all.

The filter characteristics of the axon would vary with its diameter which in turn might be a function of the recency of signals passing down that axon, or even, perhaps, of the activation of immediately environing axons. If such time factors and field interactions play a crucial role, there is no reason to hope that the information processing on the neurophysiological level can be described in a digital formalism or, indeed, in any formalism at all. In 1966, Walter Rosenblith of M.I.T., one of the pioneers in the use of computers in neuropsychology, summed up the situation: We no longer hold the earlier widespread belief that the so-called all-or-none law from nerve impulses makes it legitimate to think of relays as adequate models for neurons.

Key Concepts

• The latest suggestion from Jerome Lettvin of M.I.T. is that the diameter of the axon may play a crucial role in processing information by acting as a filter.
• An individual neuron fires at a certain frequency. The diameter of its various axon branches would act as low pass filters at different cutoff frequencies. Output from a given cell would then produce different frequencies at different terminals.
• The filter characteristics of the axon would vary with its diameter which in turn might be a function of the recency of signals passing down that axon, or even, perhaps, of the activation of immediately environing axons.
• If such time factors and field interactions play a crucial role, there is no reason to hope that the information processing on the neurophysiological level can be described in a digital formalism or, indeed, in any formalism at all.

Context

Introduction of a specific, contemporary neurophysiological proposal (Lettvin) that emphasizes temporal filtering and field effects, used by Dreyfus to argue against digital or even fully formalizable descriptions of neural information processing.