It goes without saying that neural networks are complex; the circuitry of the our minds involve interactions between thousands of interlinked networks. And that complexity is part of the reason that artificial neural networks are often unable to replicate human cognition — they’re slower than biological networks, and use far more energy. It’s whyGoogle’s DeepMind AI has only just beat a grandmaster at Go, and why Harvard announced plans to build an AI as fast as the human brain but hasn’t managed it… yet.
So when these networks, and the neurons they’re made up of, are damaged, it can be catastrophic. Patients with central nervous damage can experience problems with language, memory and perception.
There’s some hope, though — researchers from McGill University have this week announced a way to create new functional connections between neurons for the first time. Growing over 60 times faster than neurons do naturally, the connections are indistinguishable from biologically-generated counterparts, and it could provide a way of regenerating the central nervous system, providing new types of surgery and therapy for those with damage or disease.
There are other forms of communication within the brain, something a study from the Ernst Strüngmann Institute (ESI) for Neuroscience in Frankfurt looked to explore. They researched the processes by which the brain understands information — “bottom up” and “top down”. These processes help the brain organise information within context, to make predictions about behaviour and to steer attention to whatever has been judged as important. It happens automatically — the sudden appearance of a threatening stimulus, for example, is processed through bottom up and top down channels.
What the ESI team found is that the visual cortex in humans uses different frequency channels depending on the direction in which information is being transported — something that may help understand the cause of psychiatric illnesses in which channels appear to be mixed up. In schizophrenia, for example, the top-down flow does not interact with the bottom-up flow in a normal way.
“A healthy person can distinguish between sensory inputs and their interpretation produced in higher areas. For example, they can see facial features in a cloud without thinking that the cloud is a face. Schizophrenic patients may think the face is real, potentially taking the top-down interpretation for a bottom-up sensation,” said study author Pascal Fries.
Schizophrenia hit the news again this week, as a landmark genetic study found that a person’s risk of schizophrenia depends to some extent on their genes — the first time a biological process was linked to the psychiatric disorder. The study, conducted by researchers from the Broad Institute’s Stanley Centre for Psychiatric Research, Harvard Medical School and Boston Children’s Hospital, found that risk of schizophrenia is higher in people who inherit genes — the C4 gene — related to “synaptic pruning”, the elimination of connections between neurons.
Mixed up processing isn’t the only thing that can affect the way we perceive things, though — fear can do it, too. A study from Ruhr University Bochum in Germany found that stress inhibits the perception of complex spatial information — a phenomena they say lies in the processing of information in the hippocampus, an area of the brain heavily influenced by the stress hormone cortisol. Another study, at Northeastern University, found that ‘freezing’, which was considered to be the natural fear response, may not be the only response to terror. Instead, ‘darting’ gave subject rats “cognitive flexibility”, allowing them to escape.