Why intracranial electrical stimulation of the human brain suggests an essential role for prefrontal cortex in conscious processing: a commentary on Raccah et al.

We read with interest the synthesis by Raccah and colleagues on the perturbations of consciousexperience elicited by intracranial electrical stimulation (iES) of the prefrontal cortex (PFC) in awakeneurosurgical patients. The main outcome of the review is the report that iES of the PFC shows fewercausal changes of conscious experience than iES of posterior sensory areas. The authors interpretedthis finding as a challenge to neuroscientific theories of conscious processing that attribute a centralrole to PFC, such a Global Neuronal Workspace Theory (GNWT) and Higher Order Thought theory(HOT). We agree that this anterior vs posterior issue may offer an experimental challenge that thepresent theories of conscious processing have to take up, and we provide here a list of seven majorpoints that begin to specify a GNWT account for the observations compiled by Raccah and colleaguestogether with more recent, unmentioned, data.

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Does the Prefrontal Cortex Play an Essential Role in Consciousness? Insights from Intracranial Electrical Stimulation of the Human Brain

Journal of Neuroscience ◽

10.1523/jneurosci.1141-20.2020 ◽

2021 ◽

Vol 41 (10) ◽

pp. 2076-2087

Author(s):

Omri Raccah ◽

Ned Block ◽

Kieran C.R. Fox

Keyword(s):

Electrical Stimulation ◽

Prefrontal Cortex ◽

Human Brain ◽

Essential Role ◽

Stimulation Of

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Changes in Prefrontal Cortex–Thalamic Circuitry after Acoustic Trauma

Biomedicines ◽

10.3390/biomedicines9010077 ◽

2021 ◽

Vol 9 (1) ◽

pp. 77

Author(s):

Kristin M. Barry ◽

Donald Robertson ◽

Wilhelmina H. A. M. Mulders

Keyword(s):

Electrical Stimulation ◽

Prefrontal Cortex ◽

Auditory System ◽

Acoustic Trauma ◽

Neuron Activity ◽

Compensatory Mechanism ◽

Efferent Connections ◽

Medial Geniculate ◽

Central Auditory Pathways ◽

Stimulation Of

In the adult auditory system, loss of input resulting from peripheral deafferentation is well known to lead to plasticity in the central nervous system, manifested as reorganization of cortical maps and altered activity throughout the central auditory pathways. The auditory system also has strong afferent and efferent connections with cortico-limbic circuitry including the prefrontal cortex and the question arises whether this circuitry is also affected by loss of peripheral input. Recent studies in our laboratory showed that PFC activation can modulate activity of the auditory thalamus or medial geniculate nucleus (MGN) in normal hearing rats. In addition, we have shown in rats that cochlear trauma resulted in altered spontaneous burst firing in MGN. However, whether the PFC influence on MGN is changed after cochlear trauma is unknown. We investigated the effects of electrical stimulation of PFC on single neuron activity in the MGN in anaesthetized Wistar rats 2 weeks after acoustic trauma or sham surgery. Electrical stimulation of PFC showed a variety of effects in MGN neurons both in sham and acoustic trauma groups but inhibitory responses were significantly larger in the acoustic trauma animals. These results suggest an alteration in functional connectivity between PFC and MGN after cochlear trauma. This change may be a compensatory mechanism increasing sensory gating after the development of altered spontaneous activity in MGN, to prevent altered activity reaching the cortex and conscious perception.

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