I Predicted The Existence Of Component Five

27 February, 2016
The discovery of a "music area" in the human primary auditory cortex by Norman-Haignere et al was accompanied by the discovery of a "language area", one which responds to language independently of specific language. This response to language is very similar to the response to "speech-like sounds" which I hypothesised as both an evolutionary pre-cursor to the response to music, and as an important component of the early stages of infant language acquisition.

The Discovery of a "Music Area" (or something close to it) in the Human Brain

In Distinct Cortical Pathways for Music and Speech Revealed by Hypothesis-Free Voxel Decomposition, authors Sam Norman-Haignere, Nancy G. Kanwisher and Josh H. McDermott announced the discovery of a set of neurons in the human primary auditory cortex which primarily respond to music.

There are various caveats to this discovery, including the limitation that activity of neurons in the human brain is primarily observed via fMRI. Subject to choice of magnetic field strength (a fairly standard 3 Tesla machine was used in the research reported in the paper), each voxel (ie each pixel in the image) represents "hundreds of thousands" of neurons, so our current best views of human brain activity are very fuzzy.

The Six Responses

The authors used a statistical approach which allowed them to identify six distinct components of response in the primary auditory cortex, each component defined by the aspect of sound that it responds to:

  1. Low frequency sounds
  2. High frequency sounds
  3. Fast temporal modulation and coarse-scale spectral modulation
  4. Fine spectral modulation and slow temporal modulation
  5. Speech
  6. Music

The statistical approach used allowed the authors to identify components of response where different components might co-exist within individual voxels. Of course such a voxel represents "hundreds of thousands" of neurons, and one might suppose that individual neurons within such voxels belong primarily to only one of the six response components (but verifying that supposition is way beyond the capability of any existing imaging technology).

Response Component Six: Music

The most significant of the six response components is the last one, component six, which is a response to music. It is significant because this is the first time anyone has convincingly identified a music-specific processing region in the human brain (although past work has found limited evidence for localisation of music processing in the brain, as the paper's authors list in the discussion section of their paper).

Response Component Five: Language

But also of interest is component five, which is a response to the sounds of speech.

What is particularly of interest is the non-language specific nature of this response. That is, component five is a response to the sounds of spoken language, whether or not that language is the native language of the listener.

As it happens, this response is a very close match to the response which I have hypothesized as both an evolutionary pre-cursor to our response to music, and also as a component of the mechanism of language acquisition, where it matters simply for the infant learning language to identify which sounds are language and which sounds aren't language.

I first published this hypothesis about a response to language-like sounds in my blog article Music and Daydreaming (6 May 2015), and I elaborated further on it in later articles, in particular Music, Twin Speak and the Language Prototype, Music and the Language Prototype in a Venn Diagram, Music: The Third Reality and Language, Displacement, and the State of Mind Induced by Music.

Where Do We Go From Here?

My theory does make one prediction about responses to speech and music in infants and in older humans (be it older children or adults), which is:

Apparently it is possible to do research involving fMRI scans of young babies, so this is a prediction that could be tested in practice.