Prefrontal cortex, time and consciousness

Authors:

• Robert T. Knight

• Marcia Grabowecky

Date: 2000

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Abstract:

A central feature of consciousness is the ability to control the fourth dimension, time. Humans can effortlessly move their internal mental set from the present moment to a past remembrance and just as easily project themselves into a future event. It is proposed that this capacity to extract oneself from the present and fluidly move forward or backward in time is dependent on the evolution of the human prefrontal cortex. Prefrontal cortex modulates activity in multi-modal association and limbic cortices through widely distributed inhibitory and excitatory pathways. Prefrontal cortex also has a selective bias to novelty, crucial for detecting change and hence for the correct temporal coding of events. These extensive modulatory pathways coupled with an intrinsic link to temporal coding provide a mechanism for rapid engagement of distributed neural networks critical for seamless transitions through the time continuum. Support for this hypothesis is found in the fact that prefrontal damage results in a failure in the ability to extract oneself from the present. Indeed, the hallmark of the severe prefrontal syndrome is persevatory and stimulus-bound behavior--a classic example of a failure in temporal control.

Escape from linear time: prefrontal cortex and conscious experience

Authors:

• Robert T. Knight

• Marcia Grabowecky

Date: 1995

Abstract:

Insights into the brain mechanisms of conscious experience are provided by the study of neurological patients / patients with prefrontal damage exhibit deficits in behaviors that are crucial for normal conscious experience / problems with inhibitory control of external sensory inputs and internal cognitive processes, coupled with abnormalities in the detection of novel events, lead to a cascade of behavioral deficits / reviews neuropsychological and neurophysiological evidence linking prefrontal cortex to these deficits and to conscious experience.

Role of human prefrontal cortex in attention control

Authors:

• Robert T. Knight

• Marcia Grabowecky

Date: 1995

PubMed: 7771302

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Abstract:

Without a functioning dorsolateral prefrontal cortex, humans are stimulus bound and have little confidence in their ability to interact with the environment. Deficits in inhibitory control of external and internal processes coupled with impaired temporal coding of stimuli and detection capacity for novel events leave the patient functioning in a noisy internal environment without critical spatiotemporal cues. Some of these proposals are similar to those of Nauta (104). Based on connectivity of the prefrontal cortex, Nauta suggested that this region was ideally suited to generate and evaluate internal models of action. It is proposed that, in addition to this generation function, the prefrontal cortex is crucial for detecting changes in the external environment and for discriminating internally and externally derived models of the world. This chapter has described a cascade of deficits that result from damage to the dorsolateral prefrontal cortex. Awareness of the sensory world, and of the apparent stream of internal and external events, is impaired by deficits in novelty detection. Changes in the world, internal or external, may not be noticed in a noisy internal milieu. These deficits contribute to impaired reality monitoring and to a subsequent lack of confidence in behavior. An inability to bridge temporal gaps and temporally sequence internal events, together with deficits in inhibitory control systems, contribute to an impairment in the ability to generate coherent representations of alternate or counterfactual realities.