Why do some neurons respond so selectively to words, objects and faces?

February 27, 2014
Why do some neurons respond so selectively to words, objects and faces?

Some neurons in the brain respond to words, objects and faces in a highly selective manner, consistent with the so-called 'grandmother cell' theory whereby a particular neuron activates when a person sees, hears or otherwise senses a specific entity, such as his or her grandmother. For example, a neuron in a human was found to respond to images of Jennifer Aniston but not to other people, objects or scenes.

So why do neurons respond in this remarkable way? A new study by Professor Jeff Bowers and colleagues at the University of Bristol argues that highly selective are well suited to co-activating multiple things, such as words, objects and faces, at the same time in short-term memory.

The researchers trained an to remember words in short-term memory. Like a brain, the network was composed of a set of interconnected units that activated in response to inputs; the network 'learnt' by changing the strength of connections between units. The researchers then recorded the activation of the units in response to a number of different words.

When the network was trained to store one word at a time in short-term memory, it learned highly distributed codes such that each unit responded to many different words. However, when it was trained to store multiple words at the same time in short-term memory it learned highly selective ('grandmother cell') units – that is, after training, single units responded to one word but not any other. This is much like the neurons in the cortex that respond to one face amongst many.

Why did the network learn such highly specific representations when trained to co-activate multiple words at the same time? Professor Bowers and colleagues argue that the non-selective representations can support memory for a single word, given that a pattern of activation across many non-selective units can uniquely represent a specific word. However, when multiple patterns are mixed together, the resulting blend pattern is often ambiguous (the so-called 'superposition catastrophe').

This ambiguity is easily avoided, however, when the learns to represent words in a highly selective manner, for example, if one unit codes for the word RACHEL, another for MONICA, and yet another JOEY, there is no ambiguity when the three units are co-activated.

Professor Bowers said: "Our research provides a possible explanation for the discovery that single neurons in the cortex respond to information in a highly selective manner. It's possible that the cortex learns highly selective codes in order to support short-term memory."

The study is published in Psychological Review.

Explore further: Mapping objects in the brain

Related Stories

Mapping objects in the brain

December 20, 2013

A brain region that responds to a particular category of objects is found to consist of small clusters of neurons encoding visual features of these objects.

Researchers discover key to the reduction of forgetting

December 12, 2013

A team of neuroscientists has found a key to the reduction of forgetting. Their findings, which appeared in the journal Neuron, show that the better the coordination between two regions of the brain, the less likely we are ...

Clouds in the head

May 21, 2013

Many brain researchers cannot see the forest for the trees. When they use electrodes to record the activity patterns of individual neurons, the patterns often appear chaotic and difficult to interpret.

Recommended for you

Neuro chip records brain cell activity

October 26, 2016

Brain functions are controlled by millions of brain cells. However, in order to understand how the brain controls functions, such as simple reflexes or learning and memory, we must be able to record the activity of large ...

Can a brain-computer interface convert your thoughts to text?

October 25, 2016

Ever wonder what it would be like if a device could decode your thoughts into actual speech or written words? While this might enhance the capabilities of already existing speech interfaces with devices, it could be a potential ...

The current state of psychobiotics

October 25, 2016

Now that we know that gut bacteria can speak to the brain—in ways that affect our mood, our appetite, and even our circadian rhythms—the next challenge for scientists is to control this communication. The science of psychobiotics, ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.