Unconscious attention manifested in non-averaged human brain potentials by optional short-latency cognitive...

The cognitive unconscious is distinct from the psychoanalytic unconscious and is defined in experimental psychology as including mental processes which can influence behavior while remaining outside phenomenal awareness. We analyzed its physiological basis in scalp-recorded averaged and non-averaged human brain potentials evoked by near-threshold somatic (finger) sensory stimuli while the subject attended a non-somatic task. The early N20 electrogenesis in parietal area 3b, which was present and did not change across conditions, is thought to reflect automatic procedural processing of stimulus features. Short-latency cognitive P40, P100 and N140 electrogeneses were identified in non-averaged responses by assessing their characteristic scalp topographies with the Z method. They were found to be present intermittently in only 4-16% of the trials, respectively. These results establish that the unattended finger inputs are occasionally submitted to incomplete optional cognitive processing in the parietal cortex. There was no associated P300 electrogenesis which is taken to substantiate the view that these sensory inputs remained outside the subject's awareness. On this basis, we propose to relate the psychological phenomena of 'unconscious attention' and implicit perception to characteristic physiological mechanisms in the human brain, namely the incomplete parallel cognitive processing of sensory inputs which remain on the fringe of the consciously attended objects or events.