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Dissociation of neural circuitry for conscious and unconscious processing of personally-significant faces. María A. Bobes Center for Neuroscience, Cuba.

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Presentation on theme: "Dissociation of neural circuitry for conscious and unconscious processing of personally-significant faces. María A. Bobes Center for Neuroscience, Cuba."— Presentation transcript:

1 Dissociation of neural circuitry for conscious and unconscious processing of personally-significant faces. María A. Bobes Center for Neuroscience, Cuba

2 Many different types of information derived from faces: race, sex, emotional-expressions, age, identity Bruce and Young, 1986 Assoc. prospag..

3 Faces tell us who is who (e.g. good and bad or friends and enemies) Face identity has emotional content ! Emotion-from-identity Face identity also offers socio-emotional information

4 Tranel, Damasio & Damasio, JOCN, 1995, 7:432 Double dissociation between identity recognition and emotional processing of face identity Prosopagnosia Medial orbitofrontal damage

5 Capgras Modified Bruce & Young model to accommodate double dissociations (Ellis et al) Assoc. prospag.. Medial Orbitofrontal

6 Limitations of purely cognitive models Theories are under-constrained They have poor contact with neurophysiological data The posited pathways are not informed by neuroanatomy Early attempts to make the connections were heavily criticized because they were based on incomplete data & were difficult to test (recommendation then to ignore anatomy)

7 FFA OFA Hasson, Harel, Levy, & Malach, Neuron, 2003 => STS

8 Posterior Superior Temporal Sulcus (pSTS) Core Area of the Face Processing System (Haxby et el, 2000) Extended system for familiar faces?

9 What is unclear Are there additional areas involved? What are the connections of these areas What is the functional contribution of each area How brain damage disrupt this circuitry fMRI  correlation DTI. Tractography Lesions  causal inferences

10 fMRI Event related design   St Duration: 1s  SOA: variable between 4 and 6 s 3 sessions. Each session: 15 acquaintance faces, 15 learned faces, 30 unknown faces 45 houses. Target (40 %) Standard (60 %) 1.5 Tesla TR= 2 16 slices Statistical Analysis: SPM5+ in- house scripts

11 fMRI analysis ROI localization of areas responding to faces (faces > houses) Finite impulse response estimations for each stimuli condition in each ROI Permutation t test over the FIR. (Time characterization)

12 FFA (L/R) OFA (L/R) AIT (L/R) Post. Cing.(L/R) Medial Orb.fr. (L/R) Insula Dorsolateral Frontal (L) Inferoparietal (L) Activation for faces >houses Regions of Interest ROI Structural face processing Emotional processing Attention working memory Semantic processing

13 FFA d OFA d FFA d OFA d Acq vs 0 Unfam vs 0 Acq vs Unfam OFA d FFA d

14 OFA d Fam vs 0 Desc vs 0 Fam vs Desc FFA d OFM d

15 Unknown faces > Houses FFA mOFC OFA STS acquaintance > unknown faces PC Group analysis AIT

16 To Summarize BOLD responses to faces of acquaintances were of larger amplitude and longer duration than to faces of strangers in all ROI, especially in the right hemisphere. This differential responsiveness increases as one moves from extrastriate areas to PC to lateral and medial prefrontal cortex. There are striking differences in BOLD time- courses in different ROI and interestingly for different conditions in the same ROI (excludes local vascular factors or regional differences in the coupling of neural activity). This suggests that different BOLD time-courses could reflect distinct neural patterns of activity.

17 Basser et al., 1999 Mori et al., 1999 Attempt to ‘connect’ voxels on basis of directional similarity of coincident eigenvectors

18 Catani, Brain, 2005 Classical DTI tractography: tracts defined by ROIs in white matter: -Good “in vivo” reproduction of tracts found by “post-mortem” dissection -Unfortunately relationship with functional areas (e.g. OFA, FFA) not precise -Gets “lost” or stops in GM SLF

19 Probabilistic DTI-tractography seeded with fMRI data A Monte Carlo simulation (n=200) is run at each seed voxel and at every step of the path construction a direction randomly drawn from a distribution). Validity measure calculated for all paths. Seed ROIs can be placed in GM Paths can penetrate GM Here we used clusters of fMRI activation specific to faces as seeds for the tractography Average of validity measures for all paths coming from the same ROI and reaching any voxel was used as an index of connectivity between the ROI and the voxel.

20 Seed ROI defined by fMRI OFA FFA Voxelwise, T-test, n=30, of connectivity index, FDR=0.05 Additive color map

21 Visual retinotopic cortex (v4) Occipital Face Area (OFA) Fusiform Face Area (FFA) Anterior Inferior Temporal (AIT) ( pSTS) mOrF Modified model of the Face Processing System SLF? CP lOrF? IFL IFOF

22 Summary of new findings from normal subjects 1.Core areas have larger BOLD responses to familiar faces but ERPs elicited in these areas are not affected by familiarity: Suggests feedback from later activated areas. 2.The extended face processing system for familiar faces includes the posterior cingulate and medial orbitofrontal cortex. 3.DTI-tractography seeded by fMRI data suggest a massively parallel face processing system, less sequential than posited in original models. 4.V4, OFA and FFA all feed in parallel into the Inferior longitudinal fasciculus and the Inferior Fronto- occipital fasciculus.

23 Are all these areas necessary ? Need for lesion studies

24 Brain injury / bilateral subdural hematomas (trauma). Neuropsychology: normal except face recognition Basic face processing relatively intact (Benton, Bruyer and Warrington test batteries). Dense associative prosopagnosia (zero recognition of famous people or acquaintances), cannot learn new faces Severe bilateral damage to ventral occipito-temporal cortex. Case F.E. ( 69 year old male) Person identification relies on voice, gait, clothing LR

25 ns p< /14 (57 %) 12/14 (86 %) 10/14 (71 %) Which face is more trustworthy ? Which face is nicer ? Which face is more trustworthy ? Which face is nicer ? Forced choice face selection Bobes et al, COGNITIVE NEUROPSYCHOLOGY, 2004, 21 Unknown Acquaintance (family) p<0.008 Is more familiar ? Implicit Implicit Overt

26 Skin Conductance Response (SCR) F.E. presented larger skin conductance responses to familiar than to unfamiliar faces. Bobes et al, COGNITIVE NEUROPSYCHOLOGY, 2004 Acquaintances unfamiliar

27 Voxel-wise Hotelling T2 test, using vector of intravoxel GM, WM and SCF concentration, contrasting FE vs. 237 control FDR threshold q<0.01 R L

28 % Damaged voxels in cortical regions defined by AAL atlas

29 Patient FE. ER-fMRI Acquaintances, Unfamiliar faces, Houses ROI (faces > houses) Finite impulse response estimations for each stimuli condition in each ROI Statistical comparison of the patient´s response to that of the sample of normal controls (Crawford et al, 2006)

30 OFA FFA OFA Left Right x=44y=-78 z=-14 1

31 PC CA mOFC x=0y=34 z=10 Left Right

32 FE:Left mOFC Controls> FE

33 Voxel-based tractography (OFA seeds) deficit analysis: voxel-wise ttest, FE vs 30 controls, FDR q=0.01 Deficits in the territory of the right and left ILF Method limited by large variance of values in some voxels control subjects

34 >70 % controls Only F.E. Overlap F.E. & controls Combined DTI/fMRI: Probabilistic Tracts with group OFA seeds for controls and individual OFA seeds for F.E. IFOF Apparently preserved (more on the on the left ) Lower branches of IFL leading to AIT cortex and MTL are more affected

35 Visual retinotopic cortex (v4) Occipital Face Area (OFA) Fusiform Face Area (FFA) Anterior Inferior Temporal (AIT) ( pSTS) mOrF SLF? CP lOrF? IFL IFOF Residual face processing system in FE X X X X X

36 Visual retinotopic cortex (v4) Occipital Face Area (OFA) Fusiform Face Area (FFA) Anterior Inferior Temporal (AIT) ( pSTS) mOrF SLF? CP lOrF? IFOF Residual face processing system in FE X X X

37 Visual retinotopic cortex (v4) Occipital Face Area (OFA) Fusiform Face Area (FFA) Anterior Inferior Temporal (AIT) ( pSTS) mOrF ERPs ? Time course of activation SLF? CP lOrF? IFL IFOF

38 Newly-Learned Faces Faces of unknown persons artificially learned in the lab Unique Identity Memory engrams Unique identity based on face structural information Affective significance Semantic Information Similar visually familiarity Different emotional value Acquaintance faces Faces of relatives and very close friends

39 ERP paradigm 120 channels Hz Onset latency  St Duration: 1s  SOA: 2 s Two blocks : Random presentation of 16 target known faces and 75 standard unknown faces. In one block known faces were acquaintances and in the other, newly-learned faces. Task: To discriminate between familiar (acquaintance or learned) and unfamiliar faces by pressing a key Subjects: 15 normal adults (7 F and 8 M), ages between 21 and 32

40 P300 N170 An index of early structural analysis of faces An index ofthe availability of relevant memories for people. An index of the availability of relevant memories for people. P3b. (parieto-central) P3a. (frontally distributed)

41 Learned Faces (LF) in normal subjects. Target LF Standard UF No difference in N170 (structural processing) P3b. Conscious processing of familiarity

42 Acquaintance faces (AF) in normal subjects Target AF Standard UF No difference in N170 (structural processing) P3b. Conscious processing of familiarity Additional P3a. Emotional processing of identity

43 A Newly-learned ms B Acquaitances ms C Acquaitances ms

44 Temp-parietal Polo temp Frontal inf. Frontal dorsal Temp-parietal Polo temp Frontal inf. Frontal dorsal OFM Amigdalas Polo temporal, Insula A) P3b. Newly-learned B) P3b. Acquaitances C) P3a. Acquaitances Current source stimation BMA mode.l Average Brain MNI.

45 Summarizing The effect of familiarity appears after 300 ms once the structural processing (indexed by N170 has been completed) Learned faces evoke only the parietal positivity Acquaintance faces evoke two different components: a large positivity widely distributed and maximal at parietal sites, and an earlier positivity restricted to frontal sites, which is probably generated at OFM and amygdalas.

46 ERPs. P300 0 % hits Bobes et al, COGNITIVE NEUROPSYCHOLOGY, 2004, 21 P3a adicional: Procesamiento emocional de la identidad Target AF Standard UF No difference in N170 (structural processing) An early and fronto-central P3 (P3a). Emotional processing of identity No P3b. (Conscious processing of familiarity)

47 Metodo. BMA Volumen. RMN sujeto FE OFM, amigdalas, polo temporal FE. Estimación de fuentes intracraniales. P3a o P3b? Las fuentes generadoras de P300 en FE coinciden con las de P3a en normales.

48 ERP The processing of emotion from identity does not necessarily occur before identity have been consciously detected. Covert recognition of familiar faces in prosopagnosia evoked the P3a component generated in emotional system

49 Conclusions 1. FFA is not necessary for covert recognition of familiar faces which could be enabled by OFA. Previous work (Rossion et al) has show that FFA activation is not sufficient for familiar face recognition. 2. OFA and med OrbitoFrontal cortex serve as hubs for covert (unconscious) recognition 3.Prosopagnosia not only due to lesion of “core face areas” but also a disconnection syndrome (IFL disruption) that blocks conscious recognition

50 Conclusions 4.Unconscious recognition could be mediated by the Inferior Occipito-Frontal Fasciculus or by more indirect pathways via the SLF or the Cingulate fasciculus. 5.Multimodal neuroimaging of neuropsychological cases is a powerful constraint for models of cognitive processing. 6.More effort is needed to develop of statistical techniques for multi-modal image comparison of singles cases to normal controls.

51 Research team Habana, Cuba Maria A. Bobes Lorna Garcia Yasser Iturria Ileana Quiñones Yusniel Santos Lester Melie Pedro Valdes Hernandez and many others from CNEURO Medellin, Colombia Francisco Lopera Jose Ascencio


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