Near-death experiences: A neurophysiologic explanatory model

Prior hypotheses as to the etiology of near-death experiences (NDEs) have been limited to psychiatric explanations or brief discussions of endorphins as causative agents. We present a neurophysiological explanation for NDEs based on their similarities with lysergic acid-, ketamine-, and hypercapnia-induced hallucinations. We believe the core NDE is genetically imprinted and triggered by serotonergic mechanisms.     

Commentary on Jansen's Paper

Karl Jansen raises a fundamental and exciting question: Is humankind's consciousness the result of neuronal function, or are there extra-cerebral aspects as well? While his neurotransmitter model of near-death experiences (NDEs) is well described, I find his supporting evidence weak. Methodological differences between studies of ketamine hallucinations and near-death experiences (NDEs) raise doubts about how similar those experiences are phenomenologically. While Jansen's model has electrifying implications, the data required to support his conclusions do not yet exist.     

Categorical perception for voicing contrasts in normal and lead-treated rhesus monkeys: electrophysiological indices

Categorical perception of voicing contrasts was evaluated in rhesus monkeys. The monkeys had been chronically exposed to subclinical levels of lead either from conception to birth, or for approximately 6 months postnatally beginning at birth, or were never exposed to lead. Auditory evoked responses were recorded at 1 year of age from scalp electrodes placed over the left and right hemispheres during stimulus presentation. A late component of the brain responses recorded from the right temporal region of all monkeys discriminated between stimuli in a categorical manner. This pattern of responses was noted to be similar to that previously reported for humans. Categorical discriminations were also noted earlier in the waveforms for control monkeys and for monkeys exposed to lead prenatally, although this discrimination pattern shifted to the left hemisphere of the latter group. No such effects were noted for monkeys exposed to lead postnatally. These results suggest that the neurocortical mechanisms associated with categorical perception for voicing information may be similar across human and nonhuman primates. However, early exposure to lead appears to alter these processes.     

Schedules using noxious stimuli. I. Multiple fixed-ratio and fixed-interval termination of schedule complexes

The termination of a schedule complex, comprising a stimulus in the presence of which brief presentations of electric shocks are scheduled, is a reinforcer. Conditions were studied under which schedule-controlled patterns of responding characteristic of fixed-interval, fixed-ratio, and multiple fixed-interval fixed-ratio schedules can be maintained in the squirrel monkey by terminating a schedule complex. The schedule of shock presentation was a critical determinant of the patterns of responding, especially under fixed-interval schedules of termination. The rates and patterns of responding under various schedules of termination of schedule complexes were generally akin to those maintained under comparable schedules of food presentation. The findings suggest a general similarity in the dynamic aspects of performances under schedules of schedule-complex termination and comparable schedules of food presentation. The schedule of reinforcement is more important than the nature of the reinforcer in the control of behavior.