A cybernetic model of brain function
An integrative model of brain function is proposed whose functional organization involves adaptive cybernetic, goal-seeking, switching, and steering mechanisms embedded in percept-action-environment loops. The brain is conceived as a network of reciprocally-connected, re-entrant loops (McCulloch, Lorente) within which circulate neuronal signals that build-up, decay, and/or actively regenerate.
The basic signals themselves are temporal patterns of spikes (temporal codes), held in the spike correlation mass-statistics of neuronal ensembles. The simplest temporal codes are interspike interval codes that subserve auditory pitch perception and somatosensory flutter-vibration. Complex temporal codes afford vectorial representations, multiplexing of multiple signals in spike trains (Lettvin) and broadcast strategies of neural coordination. We have proposed neural timing nets as time-domain alternatives to conventional rate-based connectionist architectures.
A functional mental state consists of the set of neural signals circulating in the system at any given point. Neuronal loops function as pattern-amplifiers. Under most circumstances the loop-gains are weakly-attenuating, whereas when circuits are disinhibited, loop-gains switch to weakly-amplifying. Compatible sets of neuronal signals can be mutually reinforcing and stabilizing, such that there is an ongoing autopoietic self-production of neuronal signals (pace Maturana) that can maintain steady informational states (von Foerster’s neural dynamical system eigenstates , Pask’s mutually stabilizing interactions of concepts). There are thus temporal interference patterns and pattern-resonances between mutually compatible neural signals (Lashley) that can be modeled in terms of mutually interacting, attracting temporal pattern-vectors that yield convergent meaning.
Cybernetic and informational functions can be mapped onto brain structures: sensory and motor processing to subcortical ascending and descending pathways and unimodal cortex; pattern analysis, recognition, transformation, and generation to cerebral cortex; switching of motor programs and attentional amplificative facilitation of sensory signals via disinhibition to basal ganglia, real time steering functions to cerebellum; mnemonic consolidation re-broadcast to hippocampus, goal-mechanisms to reward-based anticipatory prediction and remodelling mechanisms of midline dopamine centers.
Music may produce its manifold effects on us because it weakly impresses temporal patterns onto neural circuits that normally utilize those patterns for basic functions, thereby inducing particular kinds of mental states. Music also combines novelty and predictable structure to effectively drive reward (pleasure) circuits.
The model bears neurophenomenological interpretations. Those sets of signals that are actively regenerated in global loops that subserve working memory (Baars’ “global workspace”) determine the experiential contents of conscious awareness, whereas the ability itself to coherently regenerate neural signals is held to be the organizational requisite for waking consciousness (not unlike Pask’s concept of consciousness as organizational closure, albeit of neural signals). Circumstances that abolish awareness entirely (anesthesia, coma, seizure) disrupt this global regeneration process. Alternate states of consciousness (sleep, hypnosis, meditation, trance) involve different, more localized regenerative patterns.
Those circular-causal processes generated from within are experienced as self-generated thoughts, whereas those contingent sensory inputs that switch neural activity patterns from without are experienced as external sensations. Those autonomous sensorimotor routines that come to effectively control some aspect of the outer world become unconscious automatisms. Fields of internal vs. external causation thus may provide functional and phenomenal boundaries for the self.
TRADITIONS: NEUROBIOLOGY, EPISTEMOLOGY
- 8) Neurobiology; consciousness studies
- 3) Experimental epistemology; constructivism; philosophy of science