Hearing Faces


Brain areas that help us recognize a person’s face are very closely wired with those that help us recognize his or her voice, a new study has found.

I like to imagine that the dog is listening to Ace of Base.

In fact, the research seems to suggest that face recognition and voice recognition aren’t two separate processes at all – but instead, that they’re both components of a single process that associates incoming sensory data with multi-sensory memory structures.

As I’ve mentioned before, there’s a boatload of research showing that our senses don’t function as separate systems – they often cross-activate. Visual areas can process auditory or somatosensory (touch) stimuli; imagining a touch sensation can trigger a visual memory, and so on.

What’s interesting about this research, though, is how specific it is: it shows that brain areas specialized for recognizing faces – particularly the superior temporal sulcus (STS) – are directly wired to those specialized for recognizing voices – especially the fusiform face area (FFA).

As the Journal of Neuroscience reports, a team led by Katharina von Kriegstein at the Max Planck Institute studied the brains of volunteers in a diffusion-weighted MRI scanner – a special type of MRI scanner geared toward mapping connections between brain regions – while they looked at various faces, and listened to various voices.

When the team modeled the MRI scans using a mathematical technique called tractography, they discovered direct fibrous connections between areas known for recognizing faces and voices:

We localized, at the individual subject level, three voice-sensitive areas in anterior, middle, and posterior superior temporal sulcus (STS) and face-sensitive areas in the fusiform gyrus [fusiform face area (FFA)]. Using probabilistic tractography, we [found] evidence that the FFA is structurally connected with voice-sensitive areas in STS.

This is a surprising finding, because facial and vocal recognition areas are more closely connected than other visual and auditory processing areas – even those that work together:

It is particularly interesting that the face recognition area appears to be more strongly connected with the areas involved in voice identification, despite the fact that these areas are further away than areas which process information from voices on a more general level.

The researchers think these connections may be used to help us imagine the faces of familiar people when we hear their voices – and maybe vice-versa. The links could also provide more criteria to help us recognize people accurately.

Still, the exact nature of the information exchanged between the STS and FFA remains unclear – and that’s exactly the question the team aims to explore next. Future research may provide some intriguing clues about the connections between these pathways and disorders like prosopagnosia – the inability to recognize familiar faces – and phonagnosia – the inability to recognize familiar voices.

Another interesting experiment – which no one (so far as I know) has proposed – would be to play voice recordings for volunteers, then have them describe the facial characteristics of the speakers they picture. I’d gladly contribute a Barry White impression… ya know, in the interest of Science and all.

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