Neural Bases Ch 9: Consciousness & Disorders of Consciousness

Ch9 LO 1: define consciousness, core consciousness and extended consciousness

• Consciousness: the ability to be aware of self and surroundings (Damasio & Meyer 2009); a continuum of wakefulness, awareness, responsiveness, higher cognitive functions
• Core: sense of ourselves and objects in the here and now, and their relationship
• Extended: sense of ourselves in the flow of time (autobiographical self); depends on long-term memory and on core consciousness

Ch9 LO 2: list and describe the primary neurological structures involved in consciousness

• Reticular activating system (RAS): web-like nuclei in the brainstem core; 4 groups (glutaminergic, monoaminergic, cholinergic, autonomic)
• RAS projects (via intralaminar thalamic nuclei) to the cerebral cortex → cortical arousal, wakefulness, consciousness
• Damage → coma

Ch9 LO 3: list and describe two tools for tracking level of consciousness

• Glasgow Coma Scale: 15-point scale of eye, verbal, motor responses; 13-15 mild, 9-12 moderate, 3-8 severe, <8 coma
• Rancho Levels of Cognitive Functioning: 10 levels tracking emergence from coma (I lowest) to independence (X highest)

Ch9 LO 4: articulate the levels of core and extended consciousness

• Subjective (internal, 1st person) vs objective (external, 3rd person) aspects
• Core = here and now; doesn't need long-term memory
• Extended = past and future self; needs long-term memory and builds on core
• Disorders range: brain death → coma → UWS/PVS → MCS → eMCS

Ch9 LO 5: list and briefly describe at least five disorders of consciousness

• Brain death: no purposeful response, no brainstem reflexes, no sleep-wake, flat EEG
• Coma: acute non-responsive state; brainstem reflexes yes, no sleep-wake
• UWS (formerly PVS): sleep-wake cycles but no purposeful response
• Minimally conscious state: purposeful response at times
• Locked-in syndrome: aware, responds with eyes, normal EEG
• Also: dementia, epilepsy, OBEs, NDEs

Ch9 LO 6: list and describe two techniques applied to disorders of consciousness

• SLP: coma stimulation: systematic stimulation of the 5 senses to speed emergence from coma
• Audiology: ABR: measures electrical activity in the auditory pathway as sound is introduced; no response needed

Why talk about consciousness in CSD?

• Speech is a voluntary, conscious motor act
• Consciousness is at the core of every time we speak
• Many patients suffer from disorders of consciousness

Speech is a voluntary, conscious motor act: define each term

• Voluntary: an act of the will
• Conscious: aware of self and others
• Motor act: movements of the body

Define consciousness (Damasio & Meyer 2009)

• The ability to be aware of self and surroundings
• Conceptualized across a continuum of wakefulness, awareness, responsiveness, higher cognitive functions

Subjective consciousness: four descriptors and list its elements

• Internal, 1st person, subjective, mental (our sense of ourselves)
• Awareness of self; perceiving sensation; experiencing working memory; recovering/displaying space-time event memories; decision-making capacity; synthesis of these

Objective consciousness: four descriptors and list its elements

• External, 3rd person, objective, behavioral (people's observations)
• Wakefulness, background emotions, attention, purposeful behavior

Core consciousness: the three senses

• Ourselves in the here and now
• Objects in the here and now
• The relationship between these objects and ourselves

Extended consciousness: what it covers and what it's called

• Ourselves in the flow of time: thinking about our past, forecasting our future
• The autobiographical self

Which kind of consciousness depends on long-term memory, and how do core and extended relate?

• Extended depends on long-term memory (core does not)
• Extended depends on core

What does reticular mean, and where is the reticular activating system?

• 'Like a web'
• A series of specialized nuclei in the core of the brainstem

Name the four groups of RAS nuclei and what each does

• Glutaminergic: activate glutamate (exciting)
• Monoaminergic: adrenaline, serotonin, dopamine
• Cholinergic: acetylcholine (hinders sleep)
• Autonomic nuclei: innervate viscera

Where does the RAS project, and what are its functions?

• Projects to the cerebral cortex
• Cortical arousal, cortical wakefulness, consciousness

What can damage to the RAS lead to?

Conditions like coma

Glasgow Coma Scale: what it is and its score bands

• 15-point scale measuring level of consciousness
• 13 or greater: possible minor brain injury
• 9-12: moderate
• Less than 9: severe
• Less than 8: coma

GCS eye opening scores (E1-E4)

• E4 spontaneous (open before stimulus)
• E3 to sound (spoken/shouted request)
• E2 to pressure (fingertip squeeze)
• E1 none
• NT not testable

GCS verbal scores (V1-V5)

• V5 oriented (name, place, date)
• V4 confused (not oriented, but coherent)
• V3 words (intelligible single words)
• V2 sounds (moans/grunts)
• V1 none

GCS motor scores (M1-M6)

• M6 obeys two-step commands
• M5 localizing (hand above clavicle to stimulus)
• M4 normal flexion
• M3 abnormal flexion
• M2 extension
• M1 none

GCS vs other indicators: mild brain injury

• GCS 13-15
• Loss of consciousness 0-30 min
• Alteration of consciousness <24 h
• Post-traumatic amnesia <24 h
• Structural: normal

GCS vs other indicators: moderate brain injury

• GCS 9-12
• LOC 30 min-24 h
• AOC >24 h
• PTA 24 h-7 days
• Structural: abnormal

GCS vs other indicators: severe brain injury

• GCS 3-8
• LOC >24 h
• AOC >24 h
• PTA >7 days
• Structural: abnormal

Rancho Levels of Cognitive Functioning: history and purpose

• Originally 8 levels, expanded to 10 for higher-level cognition
• Tracks emergence from coma to cognitive independence approximating premorbid functioning
• Level I = lowest; Level X (was VIII) = highest

Rancho levels 1-3 and assist level

• 1: no response to all stimuli
• 2: response to pain via gross bodily movement/vocalization, inconsistent
• 3: response to discomfort, inconsistent, localized with commands
• All total assist

Rancho levels 4-6 and assist level

• 4: confused, agitated, inappropriate (short attention span); max assist
• 5: confused, non-agitated, inappropriate (may respond to simple commands/habitual tasks); max assist
• 6: confused, appropriate (problem-solving issues); mod-max assist

Rancho level 7

• Automatic-robotlike, appropriate; mod assist
• Better with habitual tasks; unsafe and impulsive; decreased social awareness; can converse with minimal confusion

Rancho levels 8-10

• 8: purposeful appropriate; decreased stress tolerance, some reasoning, retains new tasks with SBA (min assist-SBA)
• 9: attention span 2 hrs, good with familiar tasks from memory (SBA)
• 10: problem solves, anticipates (modified independent-independent)

Levels of disorders of consciousness, in order

• 1. Coma
• 2. Unresponsive wakefulness syndrome (UWS)
• 3. Minimally conscious state (MCS)
• 4. Emerging from MCS

Define coma (DOC levels)

Acute non-responsive state

What did unresponsive wakefulness syndrome replace, and why?

Persistent vegetative state, due to the connotation of 'vegetable'

Covert consciousness state

Patients labeled UWS who have cognitive-motor dissociation revealed by fMRI

Reclassification arrow: order of recovery

Coma → VS/UWS → MCS → eMCS

MCS vs PVS vs coma: eye opening and spontaneous movement

• MCS: spontaneous eyes; automatic/object manipulation
• PVS: spontaneous eyes; reflexive/patterned
• Coma: none; none

MCS vs PVS vs coma: response to pain and visual response

• MCS: localization; object recognition/pursuit
• PVS: posturing/withdrawal; startle/pursuit (rare)
• Coma: posturing/none; none

MCS vs PVS vs coma: affective response, commands, verbalization

• MCS: contingent; inconsistent; intelligible words
• PVS: random; none; random vocalization
• Coma: none; none; none

Disorders vs sleep: brain death

No purposeful response, no brainstem reflexes, no sleep-wake cycle, flat EEG

Disorders vs sleep: coma

No purposeful response, brainstem reflexes yes, no sleep-wake cycle, severely depressed EEG

Disorders vs sleep: PVS

No purposeful response, brainstem reflexes yes, sleep-wake yes, severely depressed EEG

Disorders vs sleep: MCS

Purposeful response at times, brainstem reflexes yes, sleep-wake yes, variable EEG

Disorders vs sleep: locked-in syndrome (LIS)

Purposeful response yes (eyes), brainstem reflexes yes, sleep-wake yes, normal EEG

Disorders vs sleep: normal sleep

Purposeful response at times, brainstem reflexes yes, sleep-wake yes, normal sleep patterns

Brain death: preconditions

• Diffuse brain damage with coma and apnea
• Structural brain lesion
• No reversible metabolic or toxic conditions
• Treating physicians have appropriate training

Brain death: examination elements

• Coma with no responsiveness
• Absent brainstem reflexes (e.g., pupillary light reflex)
• Apnea in the presence of elevated CO2 (hypercapnea)

Brain death: process

• Findings confirmed by two separate exams
• Second exam omitted if a confirmatory test (e.g., EEG) is done
• Declared dead after the second exam or confirmatory test
• Family offered organ donation
• Record reflects results and declaration

Dementia's effect on consciousness

• Greatest effect on extended consciousness and loss of the autobiographical self (seen in early stages)
• Core consciousness affected in the later stages

Aphasia's effect on consciousness

Both core and extended consciousness are preserved

Epilepsy's effect on consciousness

Both core and extended consciousness are impaired during an epileptic episode

Out-of-body experiences (OBEs)

Sense of leaving one's own body; loss of the feeling of embodiment

Near-death experiences (NDEs)

Elaborate experiences with cognitive, affective, paranormal and transcendental elements

SLP technique: coma stimulation

• Systematic application of stimulation to the five senses: vision, hearing, smell, taste, touch
• Purpose: speed emergence from coma

Audiology technique: ABR — what, why, and how

• Auditory brainstem response
• DOC patients can't respond to traditional hearing tests (e.g., air conduction), so nonbehavioral measures are needed
• Doesn't require a response (used on newborns)
• Measures electrical activity in the auditory pathway as sound is introduced

Ch9 textbook: which reticular nuclei matter for wakefulness, and how? (textbook summary)

• Classical reticular nuclei and cholinergic nuclei
• Glutaminergic projections → intralaminar nuclei of the thalamus → much of the cortex (glutamate is excitatory → cortical wakefulness)
• Cholinergic projections to the reticular thalamic nuclei hinder sleep

Ascending reticular activating system: path (textbook summary)

Begins in the midbrain's reticular formation → radiates through the thalamus (intralaminar nuclei) → cerebral cortex, activating and coordinating it for conscious experience

Textbook: locked-in syndrome

Fully aware and conscious but locked inside a body that doesn't work

Textbook: dementia and consciousness (textbook summary)

• Wakefulness and core consciousness preserved early to middle stages, affected late (Alzheimer's)
• Extended consciousness hit early as the autobiographical self deteriorates

Textbook: epilepsy definition (textbook summary)

Recurrent, involuntary, episodic electrical storms in the brain that suddenly impair consciousness for short periods

Ch9 LO: list the mind-brain theories (materialist views) (textbook summary)

• Reductive materialism: all of life reduced to the material and naturalistic explanations
• Nonreductive materialism: experiences (e.g., beauty) can't be reduced to neurology; other processes (psychological, philosophical, theological) needed
• Constitution view: humans are material only, but differ from animals by a first-person perspective (extended consciousness)

Ch9 LO: list the mind-brain theories (dualist and idealist views) (textbook summary)

• Emergent dualism: mind emerges from many brain activities
• Holistic dualism: persons are integrated wholes
• Substance dualism: material and immaterial; immaterial can exist apart for a time
• Radical dualism: the soul is the person; the body is a mechanism it inhabits
• Idealism: all there is is immaterial; the material is created from it

Ch9 LO: articulate the two main views of personhood (textbook summary)

• Physicalism: a person is a body only, no real difference from animals; abilities/disabilities become paramount in defining personhood

• Internal essence view: body and soul, material and immaterial; something mysterious (human spirit/essence) orders and unifies the parts