Comments on: Hallucinating neural networks

By: rosko

rosko — Wed, 27 Jul 2011 05:59:46 +0000

Yes I agree that the associations in schizophrenia are more like exaggerations of normal processing than in, for example, synesthesia. In that it’s not connection of *truly* arbitrary things, more like “leaps”. For example, the “apple” to “fishing” may go like “apple”–> “apple trees” –> “Grandpa’s farm in the summer” –> “fishing at the lake”, but perceived all at once like a reflex, while a normal person’s thought train would only go where attention explicitly wills it.

I’ve listened to/read the “word salad” of some schizophrenics before, and each individual grouping of words somewhat makes sense, it is only when you try to understand it as a whole that it becomes gibberish.

By: kjmtchl

kjmtchl — Tue, 26 Jul 2011 06:55:49 +0000

Rosko, my feeling is that the excess associations observed in schizophrenia are different from those seen in synaesthesia, where there may be a lack of pruning, resulting in hyperconnectivity between normally segregated cortical areas or circuits. In synaesthesia these associations are involuntary, arbitrary pairings of various types of objects (letters and colours, words and tastes, for example). In schizophrenia, they are probably more conceptual and fluid, reflecting either a general breakdown in information flow across networks and/or altered salience processing, so that trivial connections between things assume greater significance and are factored into ongoing narratives. (Salience processing also involves dopamine signaling, which may similarly be implicated in the origins of delusions).

By: Luke Lea

Luke Lea — Mon, 25 Jul 2011 22:57:03 +0000

Damn, if I were younger I might go into neuroscience! When you write about it it starts to make sense. Have you considered neuroscience journalism?

By: rosko

rosko — Mon, 25 Jul 2011 22:29:32 +0000

And of course, it may also be that “simple” and “complex” hallucinations (i.e., swirling lines vs. the recognizable image of a person or the sound of the person’s voice) have a completely different etiology, though it appears that stimulating the same receptors can trigger both.

By: rosko

rosko — Mon, 25 Jul 2011 22:08:28 +0000

The idea of overpruning seems rather odd considering that the “broader psychosis phenotype” includes the tendency to make looser and more abundant associations between words, concepts, etc. I remember actually on GNXP there was a study mentioned where the relatives of those with schizophrenia came up with more associations to a word–like if they saw “apple”, average people might think of “oranges”, “pie”, and “tree”, while the schizophrenia relatives were more likely to think of words like “moonlight” or “fishing” that have no obvious literal connection.

Unless it’s maybe the interneurons responsible for lateral inhibition that are pruned. I remember once reading about someone making a mathematical model of 5HT2 agonist-induced visual hallucinations (like, LSD spirals dude). The key there was increased gain in the neurons, making the circuit less “overdamped” and the boundaries between adjacent cells “leaky”. This allowed for macroscopic standing or traveling waves to emerge in a 2-D layer of the visual cortex. Similar waves are observed in migraines, as far as I’m aware, which can produce hallucinatory experiences as well.