Neural Correlates of Consciousness

1. Neural Correlates of Consciousness By Charlene Campbell

2. Different Correlates of Consciousness to be Addressed • Audition • Neural Correlates of Novel sound gating • Jaaskelainen • Perspective taking • Neural Correlates of human self-consciousness • Vogeley et al. • Vision • Neural Correlates of the attentional blink • Feinstein et al, Kranczioch et al • Neural Correlates of Conscious Vision • Pins and ffytche

3. Neural Correlates Constituting Novel Sounds to Consciousness • Jaaskelainen et al

4. Jaaskelainen et al • Purpose: • Find the neural mechanisms that underlie preattentive gating awareness of novel sounds

5. Jaaskelainen et al • Methods • Use fMRI, EEG, and MEG to show brain activity when auditory stimulation occurs • auditory stimuli • Novel stimuli • Give novel stimuli alone • Standard stimuli • Give standard stimuli alone • Novel + Standard stimuli • Give novel stimuli after standard stimulus

6. Jaaskelainen et al

7. Jaaskelainen et al • Conclusion • Neurons in posterior auditory cortex are more broadly tuned on sound frequency then that of anterior auditory cortex • Processing of low-novel sounds is significantly delayed in the anterior auditory cortex • High-novel sounds are processed quickly and enter consciousness soon through stimulation of un-adapted feature-specific neurons within posterior auditory cortex

8. Vogeley et al • Neural Correlates of First Person Perspective as One Constituent of Human Self-Consciousness • Purpose • To find the neural mechanisms associated with perspective taking

9. Vogeley • Methods • A virtual seen consisting of an avatar and red balls in a room was presented by different camera viewpoints • View points were either 3PP vs 1PP or a ground view (gv) vs. an aerial view (av) • Camera viewpoints presented to normal viewers in an fMRI experiment • Task of subjects: • Count objects as seen either from avatars perspective (3pp) or from their own perspective (1pp)

10. Vogeley et al

11. Vogeley et al • Results • When taking a 3PP, there was increased activity in the precuneus, the frontal cortex bilaterally, the cerebellum bilaterally, the left temporal cortex, and the occipitoparietal cortex on the left side. • When taking a 1PP, there was increased activity in the lateral superior temporal cortex bilaterally including the insula, mesial cortical areas (both frontal and parietal), left frontal coretex and the right postcentral gyrus

12. Vogeley et al • Conclusion • Even though there are joint neural mechanisms, decision making 3PP and 1PP rely on differential neural processes.

13. First Neurobiological Accounts of Visual Consciousness • View 1 • Visual consciousness is a localized event • Zeki and ffytche showed that the difference in seeing or not seeing was dependent on the activity of a single visual area – area V5 • View 2 • Visual consciousness is a network of inter-related activity • Lumer et al showed that perceptual transitions between 2 constant stimuli correlated with activity in a fronto-parietal network of areas.

14. Consciousness as a Network • Neural Correlates of the Attentional Blink • Feinstein et al • Kranczioch et al

15. Feinstein et al • Purpose • To understand the path from sensory processes to conscious perception

16. Feinstein et al • Methods • RSVP of numbers and letters • Embedded in RSVP are T1 and T2 • T1  either odd or even string of numbers (ex. 11111 or 22222) • T2  either a neutral or aversive word • Subjects told to focus on RSVP and then state whether T1 was odd or even, and whether T2 was seen • fMRI’s were taken though out experiment

17. Feinstein et al

18. Feinstein et al • Results • (a) chart depicting the areas of the brain that showed greater activity when T2 was identified • (b) is another representation of an increase in activity when T2 was detected • (c) Shows how the anterior cingulate, frontopolar cortex, and the medial prefrontal cortex increase in activity and thus consciously perceived T2

19. Feinstein et al • Conclusions • Activation of the anterior cingulate, medial prefrontal cortex, and frontopolar cortex is involved in the conscious perception of T2 • Results support theory that consciousness is a product of interactions between many parts of the brain

20. Kranczioch et al • Purpose • Identify brain regions assumed to be involved in controlling the access of information to consciousness • Relevant conclusions of previous studies • Interference between target and mask is associated with increased activation of frontoparietal network • Includes lateral frontal, anterior cingulate, and interparietal areas

21. Kranczioch et al • Methods • A RVSP sequence of 20 capital black letters and 1 capital green letter were shown with no inter-stimulus interval • RSVP=rapid serial visual presentation • The capital green letter played the role of being a defined target that the subject should focus on. will be referred to as T1 (target 1) • The letter X was then denoted as the second target  T2 • In the experiment, subjects were required to indicate after seeing the RSVP sequence if: • T1 was a vowel • T2 was present • Responses given via a response pad

22. Kranczioch et al • Methods Side Note • T1 and T2 target relations in previous studies • In an RSVP sequence when T2 followed T1 between 200-400ms later, the detection of T2 was significantly impaired  attentional blink window • Accuracy for T2 detection was highest when immediately following T1 or at least 500 ms after T1

23. Kranczioch et al • Methods continued • fMRI’s were retrieved while sequence evaluation was taking place

24. Kranczioch et al • Results • 6 conditions were studied • Lag refers to amount of time which T2 followed after T1 • T2 detected (lag 1 100ms after T1) • T2 detected (lag 2) • T2 missed (lag 1) • T2 missed (lag 2) • T2 detected • No T2

25. Kranczioch et al • Results • (A) Regions of the brain that were active when T2 was detected and when T2 was absent • (B) Regions of the brain that were active when T2 was detected and when T2 was missed

26. Kranczioch et al

27. Kranczioch et al • Conclusion • Findings support that T2 is not detected because it doesn’t reach working memory • Targets that do not reach awareness are processed beyond a first stage of perceptual identification • Supported by findings of increased activity of inferior frontal, parietal, and frontal/anterior cingulate cortex in the T2 missed trials in comparison to the T2 absent trials

28. Pins and ffytche • Purpose: • To Identify whether neural correlates of visual consciousness are localized or distributed. • To Identify where the neural correlates are located

29. Pins and ffytche • Basic Ideas to keep in mind: • Whether the stimulus is seen or not seen indicates a difference between visual input and visual perception. • If stimulus is seen, then visual perception has taken place • Perception for this experiment is defined as a “conscious visual experience”

30. Pins and ffytche • Methods • Visual stimulus portrayed • Visual stimulus is composed of a circular sinosoidal grating of ~1 cycle/degree appearing on a grayscale background. • Each stimulus trial is composed of 5 parts • Pre-stimulus warning sound • Pre-stimulus waiting period (random variations in length of period to ensure no pre-stimulus anticipatory response) • Stimulus presentation • Post-stimulus warning sound • Post-stimulus waiting period • Every time the stimulus was seen, the participant was to indicate so by pressing a button

31. Pins and ffytche • Methods continued • For each trial a fMRI (functional magnetic resonance imaging) was simultaneously taken. • 16 axial slides parallel to the plane passing through the anterior and posterior commissures were taken every 2 sec per trial • For each trial a EP (evoked potential) was simultaneously recorded as well • EP = neurophysiological components evoked by the task

32. Pins and ffytche • Results of fMRI • Activations: • Visual Areas: • Thalamus, striate cortex, fusiform gyrus, and medial occipital lobe • Motor Related areas: • Left sensory motor cortex • Right cerebellar hemisphere • Supplementary motor cortex in both hemispheres • Auditory system • Superior temporal gyrus bilaterally in the insula

33. Pins and ffytche • Results of fMRI • Suppression: • Supra-marginal gyrus (parietal) • Posterior cingulate and parahippocampul gyrus (limbic) • In an extended region passing from supperior frontal sulcus through the medial frontal gyrus to the anterior cingulate gyrus

34. Pins and ffytche

35. Pins and ffytch • Results of EP recordings during task • Early components • High-contrast supra-threshold grating evoked a series of positive and negative waves over OL and PL • Intermediate latency components • Yes trials elicited a negative • Maximal over left parietal • Late components • A negative slow wave was present for yes trials but not for no trials or catch trials. • Maximal over left parietal lobe

36. Pins and ffytch

37. Pins and ffytche

38. Pins and ffytche • Conclusions • Activity correlating with consciousness is distributed over time • Suggest that there is a segregation in primary and secondary correlates • OL activity after stimulus presentation is likely to be the primary correlate of consciousness • PL, FL, motor and auditory regions are most likely the secondary correlates of consciousness