week 10 - Consciousness Flashcards
what is the function(s) of consciousness?
6 proposed functions -
- Associated with perceiving the environment
- Crucial role in social communication
- Role in controlling our actions
- Allows us to think about events and issues far removed from the present
- Integrating and combining numerous types of information
- Bodily self-consciousness
Consciousness - the hard problem
Why are some neural mechanisms – but not others - associated with consciousness?
Difficulty explaining relationship between physical phenomena, e.g., brain activity and experience (mental states)
Why does a given physical process generate the experience it does?
How do we assess consciousness?
Commonly rely on behavioural or introspective measures
Limited due to reliance on intervening processes – attention, language etc. which may diminish the experience itself.
Patients with brain damage may demonstrate knowledge without awareness
Actual conscious experience is much richer than our ability to report it
(Lamme, 2010)
Implications of this work
Change blindness – we substantially overestimate how much we’re aware of (Levin et al., 2002)
We use top-down processes to ‘fill in the gaps’
Gives the illusion of greater awareness
Presents a clear problem for assessing consciousness based on introspection!
Global workspace theory (Baars, 1988)
Emphasised behavioural data
Role of cortex and thalamus in conscious experience
Global neuronal workspace theory (Dehaene & Changeux, 2011)
Focused on identifying the main brain areas associated with conscious awareness.
Attention linked closely with consciousness
Assumptions of both theories
Early stimulus processing involves special-purpose unconscious processors.
Consciousness is associated with integrating information
Brain areas vary as a function of content of consciousness
Conscious awareness is determined by selective attention
Global Workspace theory -
Early processing – unaffected by conscious perception
Lamy et al. (2009); ERP study
Asked participants to indicate the location of a stimulus and indicate whether their conscious aware of its presence
Amplitude of ERP unaffected by conscious perception
Conscious awareness was associated with a late wave of activity after stimulus onset
When perception conscious, more widespread brain activity
Global workspace theory -
Integrated brain functioning
Melloni et al. (2007) tested whether integrated brain functioning is crucial to conscious awareness
Participants were presented words that were hard to perceive; brain activity for those consciously perceived (or not consciously perceived) was compared
Consciously perceived were produced synchronised neural activity
frontal, parietal and occipital areas
Global workspace theory
neural activity
4 groups
Auditory stimuli
Groups showed different levels of integrated neural activity – higher in those with more conscious awareness
Synchronised neural activity may reflect consciousness?
Could also precede it or arise as a consequence?
Global workspace theory
Brain areas
Much support for assumption that prefrontal cortex and related areas are associated with conscious awareness
Overlap of functions (consciousness, attention and working memory) controlled by dorsolateral prefrontal cortex and parietal cortex (Neghavi & Nyberg, 2005)
- Represent the fronto-parietal network
ERPs directly recorded from brain (Gaillard et al., 2009)
- Conscious awareness is associated with larger effects on activation in the frontal cortex than any other brain region
Non-correlational evidence
Brain-damaged patients (Del Cul et al., 2009)
- Damage to the prefrontal cortex impairs patients’ ability to perceive a masked number than healthy controls
TMS applied to the prefrontal cortex inhibits its functioning
Disrupting prefrontal processing, via TMS, makes participants less aware of the quality of their information processing (Rounis et al., 2010)
Global workspace theory
Attention and Consciousness
Attention without consciousness and consciousness without attention are both possible (Koch & Tsuchiya, 2012)
Unseen emotional stimuli can influence attention
- Subliminal fearful faces can produce increased amygdala activation (Troiani et al., 2014)
Assumption within the global workspace approach that conscious awareness is always preceded by attention is controversial (Pitts et al., 2018)
Change blindness and inattentional blindness
- Novel objects within visual scenes are rarely detected consciously in the absence of attention
Global workspace theory - strengths
All major assumptions have been supported
Early processing of seen and unseen stimuli is similar
Consciousness is associated with integrated brain activity
Close links between attention and conscious awareness
Conscious awareness is always preceded by selective attention
Global workspace theory - limitations
Focuses narrowly on processes for visual perception
Over-exaggeration of the role prefrontal areas play in conscious experience
Integrated brain functioning is not necessarily the neural substrate for consciousness
Psychological processes have been neglected
Neural correlates of consciousness
Attempt to link behaviour measures of consciousness to associated patterns of brain activity
Studies show activation in several widely distributed brain areas
Not all areas directly link to consciousness
Rather, support monitoring, reporting of experience (frontal areas)
Anatomical correlates seem localized to a posterior cortical ‘hot zone’, includes sensory areas (Koch et al., 2016)
Is consciousness unitary?
Mostly assume we have a single unitary consciousness
Split brain patients have “illusion of unity” (Volz & Gazzaniga, 2017)
Do they have two minds, each with its own consciousness?
Seems likely patients have two distinct streams of activity, with one accessible at any given moment (Schechter, 2012)
May be a ‘major’ conscious system – the interpreter (Marinsek & Gazzaniga, 2016) – based in the left hemisphere
Is consciousness unitary? evidence
Anarchic-hand syndrome (Verleger et al., 2011)
Patient GH, ERPs
Ability to attend to stimuli and control processing was right hemisphere
Consciousness resided in left hemisphere
Patient A.C. (Hesselmann et al., 2013)
Damage to corpus callosum
Greater conscious access to stimuli information presented to the left hemisphere
