Consciousness Flashcards
Level of consciousness
continuum between being asleep/minimal arousal to awake/aroused
Diffuse brainstem structures
State of consciousness
responsiveness to stimuli
thalamus
Content of consciousness
preception, emotion, meaning, memories
widespread regions of cerebral cortex
Consciousness components
level
state
content
all 3 needed for normal consciousness
Reticular formation
required for establishing LOC
numerous nuclei within tegmentum of brainstem
diffuse network of interconnected neurons with ascending and descending projections
Receives and modifies afferent input from all sensory modalities
Ascending reticular activating system
Lateral zone: processes afferent sensory information
NT systems: modify neuronal processing in widespread CNS areas
- norepi
- dopamine
- serotonin
- histamine
- ACh
NorEpi location (consciousness)
locus ceruleus in tegmentum of pons
projects to thalamus and forebrain
NorEpi function (consciousness)
allows focus on specific task or sensory input helps suppress less salient inputs cognitive function arousal mood attention sleep/wake state pain
Locus ceruleus lesion (consciousness)
low level of NE –> low level of arousal
Dopamine location (consciousness)
ventral tegmental area
projects to prefrontal cortex, limbic structures
Dopamine fxn (consciousness)
behavioural arousal/waking promotes locomotor and explatory behaviour towards positively rewarding stimuli motivation reward emotion drug-seeking executive function
VTA lesion (consciousness)
affect attentive arousal –> less attentive, indecisive
Serotonin location (consciousness)
Raphe nuclei
project to thalamus, cortex, other NT systems in the brainstem
Serotonin function (consciousness)
in consciousness: quiet, wakeful state
- mood, sense of well-being
- sleep
- anxiety/aggression controlled
- Neurotrophic actions –> CNS development
- mood
- appetite
- sleep/wake state
- pain
- aggression
- cognitive fxn
Serotonin deficiency (consciousness)
insomnia
anti-depressants increase serotonin
Histamine location (consciousness)
tegmentum of midbrain
projects to thalamus, cortex
Histamine fxn (consciousness)
stimulates wakefulness
ACh location (consciousness)
tegmentum of pons
project to thalamus, cortex
ACh fxn (consciousness)
increase thalamocortical activation and arousal
Types of nuclei in the thalamus
relay nuclei association nuclei others: --> alertness and attn - intralaminar nuclei - thalamic reticular nucleus (TRN)
Thalamic reticular nucleus
Gatekeeper of consciousness thin mesh of neurons immediated outside of thalamus Dense reciprocal connection with: - ARAS - other thalamic nuclei - cerebral cortical structures
Interconnected network of GABAergic neurons
Coordinates synchronous firing (40 Hz) between cortex and thalamus necessary for consciousness ( = carrying freq of consciousness)
Cortex - fxn in consciousness
establish significance and meaning
synchronous and reciprocal connections with thalamus and other cortical areas
Prefrontal and parietal cortical areas are important
Parietal area (consciousness)
attention
awareness of self
awareness of extrapersonal space
Prefrontal cortex (consciousness)
association area
executive fxn over consciousness
society/societal expectations
direction and maintaining attention morality problem-solving adjusting behaviour to social norms planning working memory deliberate decisions
Top-down attention
Volitional control over focus of attention
e.g. visual attention - illuminates objects in field of view, enhances processing
Bottoms-up attention
rapid and automatic form of selective attention
the more salient a location/object in the image, the more likely it will be noticed
Coalition of neurons
a group of synaptically coupled forebrain neurons that encode one percept, event or concept
Labile
members of a coalition reinforce each other and suppress members of competing coalitions
attention biases these competing interactions
Synchronized reciprocal firing (40Hz) with thalamus plays a role in strengthening one coalition at expense of others
