A Unified Coding Strategy for Processing Faces and Voices Galit Yovel and Pascal Belin Presented by Ellen Swanson Introduce paper As humans we are very attuned to people’s voice and faces because of the massive amount of exposure to them we have. I have a quick funny video I’ll play a little of https://www.youtube.com/watch?v=pRLTqdn52AI So immediately we know that these are no these men’s voices. But it is so funny because the facial expressions match the utterances but the voice just doesn’t. We find it unusual

Outline A little background Neurophysiological Mechanisms Neurocognitive Disorders Perceptual Coding Development and Experience Future Directions Questions I’m going to go through the paper section by section. I really liked how this paper was organized-they go through the similarities between the special processing of faces and voices in terms of… This paper seemed really interesting to me when I was picking which paper to present, it doesn’t really have anything to do with what I want to do in the future. I am interested in speech pathology for children and adults with autism. One of the struggle people with autism have is focusing on people’s faces and being able to perceive emotion from facial cues. They struggle to detect other people’s emotions in general, so this includes tone of voice. The paper doesn’t go into this at all-but possibly t could be related to the field of autism research in this way.

Faces and Voices Most socially important stimuli we process The sensory information is different, but it gives us the same type of information (age, gender, emotional state, etc.) They are processed simultaneously, which lead Yovel to wonder despite their sensory differences they may generate a similar representation in the brain Faces and Voices are very special stimuli to us. They both carry a tremendous amount of information. But the sensory information received for a face compared to the sensory information received when we hear a voice. Visual and Auditory processing are different BUT faces and voices are both special phenomena of those types of processing We receive the same type of information from both-age, gender, emotional state, identity) VOICE ACTIVITY BLURRED FACE ACTIVITY Most of the time faces and voices are processed simultaneously. This lead Yovel and Balin to wonder despite the sensory differences if they may generate a similar representation in the brain This paper approaches this question in multiple ways. They want to show that there are a lot of similarities between the cognitive and neural mechanisms of face and voice processing.

? Cher

? Elvis

? Bill Clinton

Neurophysiological Mechanisms fMRI studies have shown strong activation to faces in the following areas: occipital face area, the posterior superior temporal sulcus, and the fusiform face area fMRI studies have also shown voice selective cortical mechanisms along the anterior middle superior temporal sulcus There have been many studies conducted with fMRI that have captured brain activation during face processing. The three main areas are the occipital face area, the posterior superior temporal sulcus, and the fusiform face area. Everyone here has probably heard all about the FFA. It was mentioned briefly in this class that there is evidence out there that the FFA is an expertise area of the brain. So, someone who is a car dealer may have activation in their FFA when looking at cars. All humans are face experts, so that is why the FFA is activated in people when exposed to faces. The occipital face area recognizes individual features of the face-the nose, eyes, mouth-this plays a role in the early stages of face processing The STS is activated by biological motion. fMRI studies have also shown voice selective cortical mechanisms. The anterior middle STS is activated for voices. EEG and MEG show activation that is consistent with fMRI findings .

Neurophysiological Mechanisms This type of specialized response has also been demonstrated in Macaque monkeys Their STS is functionally and anatomically similar to humans’ Voice Selective Neurons These neural responses aren’t just in humans, it’s also been observed in Macaque Monkeys. Their superior temporal sulcus is anatomically and functionally similar to ours. fMRI studies have shown voice activation in the STS as well, these monkeys prefer vocalizations from their species over any other sounds. And these voice areas contain voice selective neurons. This is really interesting because this is evidence that mechanisms specialized to faces and voices has not emerged recently. This is evidence that it’s been part of the evolution of our brains.

Neurocognitive Disorders Prosopagnosia Phonagnosia Impairments in voice discrimination and recognition Not much is known about this disorder compared to Prosopagnosia Prosopagnosia is the inability to recognize faces. https://www.youtube.com/watch?v=dxqsBk7Wn-Y Phonagnosia is the voice version of prosopagnosia. It is the inability to recognize voices. There are two types, it could be a discrimination problem, or it could be a recognition problem. There actually isn’t a lot known about it because there haven’t been that many observable cases. This is because a lot of times people don’t realize that they even have it.

Perceptual Coding The Face Space Model Faces represented as locations in multidimensional space Faces are coded relative to an ‘average’ face Perceptual coding is an approach to how we perceive faces Faces are represented as locations in multidimensional space, and then coded relative to an average. So we see a face and then compare it to a prototype. Some of you have probably heard of exemplar and prototype theory which are methods of categorization-this is kind of like th

This is one of the faces used in the paper. It’s a weird question, but what is the opposite of this particular face? Do you think you would be able to recognize the opposite of it?

Anti-Face Which one? This type of stimuli was presented to participants and then using norm based coding we are able to have an average, prototypical face that we derive all faces from. This theory is widely accepted because it account for the fact that we recognize and discriminate the tremendous amount of faces that we do.

Perceptual Coding Same type of model for voices Recent studies have shown a similar coding system for voices. The middle represents the ‘average’ voice. These voices were compared to anti-voices. http://vnl.psy.gla.ac.uk/media.php

Development and Experience Infants prefer upright faces found within the first 24 hours of life Infants can distinguish voices It has been shown that fetuses can recognize their mother’s voice Role of Experience Our brains are specialized to faces and voices and there is evidence for this very early on in life. Infants prefer faces that are upright and that’s even been observed in the first 24 hour of life. It has been shown that infants can discriminate voices from other auditory stimuli. Infants, even fetuses can recognize their mother’s voice. This early specialized responses to faces an voices hints at an innateness for them. But babies aren’t born with the ability to perceive any face or voice-there is also a role of experience which has a lot of impact on the response to faces and voices. Perceptual narrowing is constantly taking place in the first years of life. For example-there was a study of 6 month old infants being able to distinguish monkey faces and humans faces, but then at 9 months they are not able to distinguish the monkey faces (evidence that they become more specialized for human faces) By approximately 9 months of age babies can only recognize the phonemes from there own language. https://www.youtube.com/watch?v=Ew5-xbc1HMk

Future Directions More voice tests are needed to test this idea A voice correlate to the face inversion effect There is much more research out there about face processing and how special that is. This is partly because human face recognition abilities are better than voice recognition abilities, we are more visual Because of this, in order to find more evidence between the similarities of face a voice processing more tests are needed that are correlated with the face tests out there. So this is an example of a face inversion test-Margret Thatcher

Future Directions More voice tests are needed to test this idea A voice correlate to the face inversion effect This effect shows just how sensitive we are to slight changes in faces-in this case orientation of certain parts of the face. They would want a voice correlate of something like this test-and even the authors of this paper don’t know what that would be. FACE DISTORTION VIDEO https://www.youtube.com/watch?v=VT9i99D_9gI

Lingering Questions (Mostly about Voice Processing) Do voices capture more attention than other auditory stimuli? Are there voice tests that we need face correlates for? Is the face processing system more extensive than the voice processing system in the human brain?

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