!Readings
* [Required] Block (2001) "Paradox and Cross Purposes in Recent Work on Consciousness" in Cognition Volume 79, Issues 1-2, April 2001, pp.197-219. [The HKU Library has an electronic subscription] Also in Stan Dehaene (2001) ed. The Cognitive Neuroscience of Consciousness M.I.T. Press.
!Background
* Brain state X is a neural correlate of consciousness (NCC) = there is a significant correlation between brain state X and conscious experience E. X is present if and only if E is present.
Comments
# Identification depends in part on verbal report or other forms of behavior of the subject.
# Different types of experiences will have different NCCs.
# Studies on NCC of visual experience have been more extensive.
# Correlation is not identity. Finding NCC in human might not explain consciousness in general.
!Studies on neural correlates of consciousness
Diagrams of visual areas
* Logothetis (1998) - Binocular rivalry in moneys, single cell recordings, 90% correlation in inferotemporal cortex.
* Tong, Nakayama, Vaughn, and Kanwisher (1998) - fMRI fusiform face area (FFA) responds twice as strongly to faces than non-face objects (But de Gelder & Kanwisher (1999) - patient without FFA can perceive faces as faces but impaired at identifying individual faces)
* Epstein and Kanwisher (1998) - parahippocampal place area (PPA) responds strongly to images of places including houses, weakly to non-place stimuli, not faces.
* Kanwisher - Binocular rivalry study for face-house stimulus.
* Culham et el (1999), He Cohen and Hu (1998) - Awareness of motion correlates with activity in MT/MST (medial temporal cortex/medial superior temporal cortex). Goebel, Khorram-Sefat, Muckli, hacker, & singer (1998) - mental imagery of motion.
* Grill-Spector, Kushnir, Itzchak, and Malach (2000) - Object recognition success correlates with activity in LOC (lateral occipital complex).
* Lau, Rogers, Haggard, Passingham (2004) - pre-SMA (pre-supplementary motor area) activity with attention to motor intention.
!Unconscious perception
* Tootell, Hadjikhani, and Somers (1999) - uniform gray field alternates with visual gratings of same luminance. Subjects report uniform field but V1, V2, V3, VP, V3A, V4v respons more strongly to invisible gratings.
* High level perception - Whalen et el (1998) - Amygdala activation by masked angry faces vs happy faces.
* Luck, Vogel, and Shapiro (1996) - N400 ERP shows semantic processing without awareness.
* Dehaene et el (1998) - Preparation of a motor response that depends on the analysis of a masked stimulus.
!Ventral and dorsal stream
Ungerlider and Mishkin (1982) brain-lesioned monkeys
* Ventral stream : what pathway (object recognition)
* Dorsal stream : where pathway (location and movement for action)
Milner and Goodale (1995)
* Ventral stream : conscious pathway
* Dorsal stream : unconscious pathway
Problem : awareness of visual motion correlates with activity in area MT (along dorsal pathway)
Kanwisher's proposal for NCC for visual experience
NCC has two components:
* Representations of perceptual features (e.g. "red", "line" in ventral stream) +
* Binding (in parietal lobe) of features into a representation of a spatial-temporal token ("red line on the left now")
Block's misgivings
* Perhaps it is possible to have unbound conscious experiences. (ganzfeld experience)
* Perhaps it is possible to have binding in the blind field.
* Perhaps it is attention that produced consciousness (and binding), and so binding is not sufficient for consciousness. (spatial attention often linked to the parietal lobe)
Blindsight patient GY
* GY can direct attention in the blindfield enhancing stimuli processing - Kentridge, Heywood, Weiskrantz (1999).
* GY Can also guess correctly the emotion expressed by a face in the blind field (happy/sad/angry/fearful) - DeGelder, Vroomen, Pourtois & Weiskrantz (1999).
Comments:
* Binding more important for perceptual experience of objects. But in Ganzfeld, there might be no depth information but there is still binding of color with spatial coordinates in the coronal plane.
* Dehaene et el (1998) is perhaps better evidence for unconscious binding.
* The attention hypothesis is not incompatible with the binding theory.
Access requirements
* Kanwisher "awareness of a particular element of perceptual information must entail not just a strong enough neural representation of that information, but also access to that information by most of the rest of the mind/brain."
* Dehaene and Naccache - "the long distance connectivity of these workspace neurons can, when they are active for a minimal duration, make the information available to a variety of processes including perceptual categorization, long-term memorization, evaluation and intentional action."
* But what about Sperling's experiment?
Reflexivity
Attention-based theories
Example : Prinz (2000) "A neurofunctional theory of visual consciousness" Consciousness and Cognition 9 (2), pp.243-59.
* Attention necessary for consciousness (but might not be sufficient).
* Visual consciousness a matter of attention directing information from sensory systems into short-term memory.
Further discussion:
* Mack and Rock (1998) Inattentional Blindness MIT Press.
* Milner and Goodale (1995) Discussion here
Block's objections
* Intriligator and Cavanagh (2001) "The Spatial Resolution of Visual Attention" Cognitive Psychology 43, pp.171-216. According to Block, subjects have visual experience of the lines as individually distinct even though they cannot attend individually to some of the lines.
* Aerodontalgia - perhaps there is P-consciousness depsite the lack of attention.