Towards a true neural stance on consciousness by Victor A.F. Lamme (2006) Group 10: Chi-Hang Lau, Anita Leung, Clarisse Miguel, Elisa Tsan, Alistair Wong COGS 175 Dr. Pineda 03/12/08

IntroductionIntroduction About: The Basis of Consciousness Behavioral basisBehavioral basis Neural basisNeural basis Lamme: Neural basis “on equal footing” as behavioral basis of consciousness ! –Need a more scientific method for study of consciousness

IntroductionIntroduction Problem of Consciousness debated by philosophers and scientists –Philosopher Rene Descartes: “Cogito, ergo sum” –Neuroscience: finding the “Neural correlate of consciousness” (NCC)

IntroductionIntroduction example of Split Brain Patients –Cannot report “seeing” object presented on Left Field of Vision BUT, S’s can still draw object with left hand !BUT, S’s can still draw object with left hand !  Doc these S’s have Consciousness?

IntroductionIntroduction Two Difficulties: 1. What BEHAVIORAL measures 'count' as conscious experience? 2. Conscious experience is usually coupled with COGNITIVE FUNCTIONS ONE NEEDS TO REPORT ONE IS CONSCIOUS i.e. language ability and Split Brain patientsi.e. language ability and Split Brain patients

IntroductionIntroduction Lamme: Neural basis “on equal footing” as behavioral basis of consciousness ! Need a more scientific method for study of consciousness

Measuring Conscious Experience Where do we draw the line between “conscious” and “un-conscious” experience ? –Looking at behavioral measures Somewhere between “Object Recognition” and “Localization” ? Figure 1 (Lamme, 2006)

Measuring Conscious Experience (cont.) Problems ! Difficult to distinguish a definite boundary Evidence of conscious experience in one study used as evidence against conscious experience in another study Figure 1 (Lamme, 2006)

From neural activation to visual experience Example of visual experience “Feedforward sweep” vs. “Recurrent Processing”

“Feedforward Sweep” –Signal path: Visual stimuli  retina  V1  V2  motor areas Signal only goes forward (does not go back) Feed Forward Sweep vs. Recurrent Processing Figure 2 (Lamme, 2006)

“Recurrent Processing” (RP) –Signal path: Visual stimuli  retina  V1  V2 Information sent to V1, then to V2, –then exchanged between V1 and higher area V2 Feed Forward Sweep vs. Recurrent Processing Figure 2 (Lamme, 2006)

Recurrent Processing Local RP –Info exchanged between V1 and higher areas V2, V4, and TE Widespread RP –Info further exchanged with higher Frontal areas Figure 2 (Lamme, 2006)

Recurrent Processing Exchange of information from lower areas of the brain (ex. V1 and V2) with higher areas of the brain (ex. V4, pre- frontal areas)

Recurrent Processing Exchange of information from lower areas of the brain (ex. V1 and V2) with higher areas of the brain (ex. V4, pre- frontal areas) RP necessary for consciousness –Current view of consciousness !

Table 1: A) Conflating Conscious experience with other cognitive functions Table 1 (Lamme, 2006)

B) Failures of reportability instead of conscious experience? Table 1 (Lamme, 2006)

B) Failures of reportability instead of conscious experience? Table 1 (Lamme, 2006)

B) Failures of reportability instead of conscious experience? Table 1 (Lamme, 2006)

B) Failures of reportability instead of conscious experience? Table 1 (Lamme, 2006)

B) Failures of reportability instead of conscious experience? Table 1 (Lamme, 2006)

B) Failures of reportability instead of conscious experience? Table 1 (Lamme, 2006)

B) Failures of reportability instead of conscious experience? Table 1 (Lamme, 2006)

Outstanding Questions What aspect of recurrent processing is necessary for conscious experience? –Activation of high-level neurons Experiment: Interrupt feedback signals to V1 (with TMS), while recording from face-selective IT cellsExperiment: Interrupt feedback signals to V1 (with TMS), while recording from face-selective IT cells Why would recurrent processing create conscious experience? –Difficult to answer, try looking at: NMDA receptors and theoretical significance of RPNMDA receptors and theoretical significance of RP Implications for speed-reading, eidetic memory, and recall under hypnosis

Recurrent processing sufficient for consciousness? Super et al. –Recorded monkey’s V1, and showed that recurrent interactions are needed for the monkey to report the existence of texture defined figures. –However, after raising number of catch trials, recurrent signals are present when monkey fails to report a figure percept. Figure 3 (Lamme, 2006)

Recurrent processes during inattentional blindness Results from a modified experiment originally done by Scholte et al. Figure 3 (Lamme, 2006)

Inattentional blindness = absence of conscious experience? Perhaps subjects only store in memory stimuli that held their attention. Episodic memory is considered as a measure of conscious experience. –The subject might have just “forgotten” about the stimulus after its presentation. Experiments on change blindness show that unattended stimuli are still represented in the mind in a quick instance.

Views 1.Take subject’s reports at face value –RP is insufficient for conscious experience –Consciousness is made up of attention, working memory, and language 2.Conscious experience must be viewed separately from other cognitive functions –But how to verify conscious experience without examining cognitive functions? 3.Global workspace theory of consciousness –Preconscious - “visible yet not seen”

"Taking the neuroscience argument seriously" Is there a conscious experience when recurrent processes only occur in single visual areas? Are conscious experiences dependent on activity in the frontoparietal network, or is it the recurrency?

Stimuli that affect the feedforward processes leave no impact; recurrent processing impacting stimuli does. Limit definition of consciousness specifically to ONLY Recurrent Processing? "Taking the neuroscience argument seriously"

"What do we lose, what do we gain..." Unconscious dichotomy in everyday actions may be better studied. Sets Consciousness as a layer in human action for easier examination. Definition conforms to the current data relating to conscious and neural activity Provides an easier means to measure consciousness in future experimentation.

Discussion