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fmri: What Does It Measure? Psychology 355: Cognitive Psychology Instructor: John Miyamoto 04/02/2018: Lecture 02-1 Note: This Powerpoint presentation may contain macros that I wrote to help me create the slides. The macros aren t needed to view the slides. You can disable or delete the macros without any change to the presentation.

Outline fmri what does it measure? Example of fmri study of face recognition Top down and bottom up processing Lecture probably ends here Psych 355,, Miyamoto, Spr '18 2

fmri Uses a Big Magnet This images is used with permission of the author, J. J. B. Allen at the University of Arizona. Psych 355, Miyamoto, Spr '18 Graphic Showing BOLD Contrast 3

Measuring Activation A Subtraction Measure Oxygenated Blood Control Condition Deoxygenated Blood Test Condition Brain Activity = Oxygen Concentration in Test Condition MINUS Oxygen Concentration in Control Condition Psych 355, Miyamoto, Spr '18 Details of fmri Measurement 4

fmri Dependent Measure BOLD Signal Blood Oxygen Level Dependent Signal BOC Measure Blood Oxygen Contrast Measure Psych 355, Miyamoto, Spr '18 Details of fmri Measurement 5

How Does fmri Measure Brain Activity Local neuronal activity Increased local metabolic rate Increased blood flow Increased oxygenated hemoglobin Control Condition Test Condition Uptake of O 2 less than supply Decreased concentrations of deoxyhemoglobin Increased local fmri T2* signal (electromagnetic signal) BOLD signal Blood Oxygenated Level-Dependent signal (the measured response is dependent on the level of oxygenated blood) A.k.a. hemodynamic response: Change in blood response measured over time Psych 355, Miyamoto, Spr '18 Strengths and Weaknesses of fmri 7

Strengths and Weaknesses of fmri Measures of Brain Activity Excellent spatial resolution Magnetic changes can be measured at a resolution of 1-3mm³. Temporal resolution is poor. In the 1990 s the temporal resolution was about 4 seconds. Today the temporal resolution is about 2 seconds. MRI machines impose physical limitations on the subjects. Psych 355, Miyamoto, Spr '18 Localization of Function 8

Localization of Function Specific functions are served by specific areas of the brain Cognitive functioning breaks down in specific ways when areas of the brain are damaged Brain imaging can identify areas of the brain that serve specific functions. Psych 355, Miyamoto, Spr '18 Localization of Function in FFA and PPA 9

Next: fmri Evidence for Brain Areas with Specialized Perceptual Functions O'Craven, K., & Kanwisher, N. (2000). Mental imagery of faces and places activates corresponding stimulus-specific brain regions. Journal of Cognitive Neuroscience, 12, 1013-1023. FFA: Fusiform face area. Specialized for faces. ( ventral occipito-temporal cortex ) PPA: Parahippocampal place area. Specialized for representing location info. ( ventromedial cortical region ) Psych 355, Miyamoto, Spr '18 Face Recognition: Graphic Showing Location of FFA & PPA 10

Location of the fusiform face area and parahippocampal gyrus Graphic from http://labnic.unige.ch/ nic/htms/fmri.html Parahippocampal place area (PPA) Fusiform face area (FFA) Diagram of Brain Head Facing Left Graphic from the article: Haynes, J-D., & Rees, G. (2006). Decoding mental states from brain activity in humans. Nature Reviews Neuroscience, 7, 523-534. Psych 355, Miyamoto, Spr '18 O'Craven & Kanwisher Research Hypotheses 11

O Craven & Kanwisher Research Hypotheses Research Goal: To test the claim that the fusiform face area is specialized for face perception. Prediction: FFA will be activated by face stimuli but not by location stimuli. PPA will be activated by location stimuli but not by face stimuli. Psych 355, Miyamoto, Spr '18 fmri % Signal Change in FFA & PPA 12

% Signal Change % Signal Change fmri Study of Face and Place Perception FFA: Fusiform face area. Specialized for faces. Perception PPA: Parahippocampal place area. Specialized for representing location info. Subject views a face or a place. Look at Just the Upper Half of this Graph Psych 355, Miyamoto, Spr '18 13

% Signal Change % Signal Change fmri Study of Face and Place Perception FFA: Fusiform face area. Specialized for faces. Perception PPA: Parahippocampal place area. Specialized for representing location information. Subject views a face or a place. Face stimulus activates FFA; place stimulus does not. Psych 355, Miyamoto, Spr '18 Look at Just the Lower Half of this Graph 14

% Signal Change % Signal Change fmri Study of Face and Place Perception FFA: Fusiform face area. Specialized for faces. Perception PPA: Parahippocampal place area. Specialized for representing location info. Subject views a face or a place. Place stimulus activates PPA; face stimulus does not. Point Out that There Is a Double Dissociation Psych 355, Miyamoto, Spr '18 15

% Signal Change % Signal Change fmri Study of Face and Place Perception FFA: Fusiform face area. Specialized for faces. PPA: Parahippocampal place area. Specialized for representing location info. Perception Face and place stimuli have opposite effects on FFA and PPA. Double dissociation! Supports claim that FFA serves face perception and PPA serves spatial perception Define Double Dissociation; Discuss Double Dissociation Psych 355, Miyamoto, Spr '18 16

Double Dissociation in Brain Imaging Suppose you are studying the function of two brain areas, A and B. Results exhibit a double dissociation if... (i) one class of stimuli activates area A and fails to activate area B; (ii) a different class of stimuli activates area B and fails to activate area A. Example: Viewing faces activates FFA but not PPA; Viewing places activates PPA but not FFA. Double dissociations are important because they provide evidence for specialization of function in different areas of the brain. (This is one type of evidence for localization of function.) Psych 355, Miyamoto, Spr '18 Summary re Physiological Methods 17

Summary Physiological methods in cognitive neuropsychology Single cell recordings Event-related potentials (ERP s) Positron emission tomography (PET) Functional magnetic resonance imaging (fmri) Localization of function identifying parts of the brain that are involved in processing specific types of stimuli or performing specific tasks. Double dissociation demonstrating that the neural response is specific to particular types of stimuli or specific tasks. Psych 355, Miyamoto, Spr '18 18 Start Perception Topic - Bottom Up & Top Down Processing

Bottom Up and Top Down Processing Bottom up processing processing of current stimulation influences what is perceived Top down processing background knowledge, learning and expectations influence what is perceived. Bottom up processing is data driven. Top down processing is theory-driven, knowledge-driven, and context-driven. Example of top down processing: Your knowledge of rectilinear solids informs your perception. Psych 355, Miyamoto, Spr '18 Examples of Top Down and Bottom Up Processing 19

Examples of Bottom Up Processes Elementary feature detection, e.g., edge detectors, bar detectors, motion detectors. The following color perception is bottom up: Your perception of the red squares is dictated by the stimulus; the perception is not influenced by prior expectations or beliefs. Similarly, the perceived motion of the blue disk is bottom up. It is controlled by the stimulus, not by your beliefs or expectations. Psych 355, Miyamoto, Spr '18 Example of Top Down Processing 20

Other Examples of Top Down Processes When people see a plane crash, at least some witnesses always claim to have seen flames coming from the engines. (Top-down when claim is false; either top-down or bottom up when it is true.) Scene understanding involves both top-down and bottom-up processing. Psych 355, Miyamoto, Spr '18 Classroom Experiment to Demonstrate Top Down Processes in Object Identification 21

Monday, 2 April, 2018: The Lecture Ended Here Psych 355,, Miyamoto, Spr '18 22