Paraphrasing/adding to the article abstract: prevailing theory suggests that long-term memories are encoded via a two-phase process requiring temporary involvement of the hippocampus followed by permanent storage in the neocortex. However this group found that, even weeks later, after the memories are supposed to be independent of the hippocampus, they could disrupt recall by briefly suppressing hippocampal CA1. The suppression must be brief; if they suppress CA1 for a long time recall works again. This suggests that, long after memory formation, the memory is not primarily stored in the hippocampus, but the hippocampus is still somehow involved in recall. The research also implicates anterior cingulate cortex in recall. Abstract after the break.
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Berger, Hampson, Song, Goonawardena, Marmarelis, and Deadwyler created a system for recording from and stimulating up to 32 neurons at once. The system learned a model to predict firing of some hippocampal CA1 neurons given some inputs from CA3, and could be “played back” later.
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Read on for a talk abstract describing aligned visual and tactile homunculi in parietal cortex.
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From the abstract: … we determine synaptic connectivity between nearby layer 2/3 pyramidal neurons in vitro, the response properties of which were first characterized in mouse visual cortex in vivo. We found that connection probability was related to the similarity of visually driven neuronal activity. Neurons with the same preference for oriented stimuli connected at twice the rate of neurons with orthogonal orientation preferences. Neurons responding similarly to naturalistic stimuli formed connections at much higher rates than those with uncorrelated responses. Bidirectional synaptic connections were found more frequently between neuronal pairs with strongly correlated visual responses….
Ho Ko, Sonja B. Hofer, Bruno Pichler, Katherine A. Buchanan, P. Jesper Sjöström, Thomas D. Mrsic-Flogel. Functional specificity of local synaptic connections in neocortical networks. Nature. 2011 May 5;473(7345):87-91. Epub 2011 Apr 10.
This dailymail article claims that the Human Brain Project, directed by Henry Markram, is pursuing a 1 billion euro grant to simulate the human brain in 12 years.
By way of Nextbigfuture, by way of Hackernews.
(pun intended). I am embarrassed to say that earlier today I remarked to a colleague that dopamine only encodes unexpected reward, not unexpected lack of reward. This is (afaik) incorrect. It has a baseline level of firing that goes down when there is an unexpected lack of reward (see fig 1 in Wolfram Schultz, Peter Dayan, P. Read Montague. A Neural Substrate of Prediction and Reward)
However, because it can only go down so far, the negative signal is clipped, which might have consequences (see Yael Niv, Michael O Duff, Peter Dayan. Dopamine, uncertainty and TD learning).
The previous article mentions that some other people think that maybe dopamine is tracking uncertainty as well as reward. This one talks about a theory that acetylcholine is related to expected uncertainty, and norepinephrine is related to unexpected uncertainty:
Angela Yu, Peter Dayan. Expected and Unexpected Uncertainty: ACh and NE in the Neocortex (huh, all those papers had Peter Dayan as one of the authors) (btw I haven’t read all of the papers I’m posting here)
Since we’re on the subject of temporal difference learning, I’ll mention that in my opinion temporal difference learning may be a model of how futures/speculators in financial markets are supposed to propagate future price changes back in time to the present (if you think of the market as a cognitive system). I haven’t formalized this idea yet, though.
this experiment claims to show that
(1) when rats are sleep-deprived, small populations of rat brain neurons can fall asleep while the rest of the rat is awake, and
(2) this may correspond to performance degradation
summary:
http://arstechnica.com/science/news/2011/04/if-you-only-feel-half-awake-you-probably-are.ars
article:
http://www.nature.com/nature/journal/v472/n7344/full/nature10009.html
i haven’t read the actual article yet…
Sahay A, Scobie KN, Hill AS, O’Carroll CM, Kheirbek MA, Burghardt NS,
Fenton AA, Dranovsky A, Hen R. Increasing adult hippocampal neurogenesis is sufficient to improve
pattern separation. Nature. 2011 Apr 3
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature09817.html
Abstract after the break.
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http://www.google.com/events/sciencefair/
“Google’s worldwide Science Fair competition …is calling for entries over the next few days. It gives kids the opportunity to join in a new kind of online science competition…offering them the chance to win … prizes including a 10-day trip to the Galapagos Islands or a $50,000 scholarship.”
They paid us to post this video of a Rube Goldberg machine (you don’t need sound, it’s just random music):
(you won’t be able to see it if you have AdBlock enabled)
