Introducing the brain: it anticipates senses (Introduction)

by David Turell , Monday, May 13, 2019, 19:50 (2019 days ago) @ dhw

When you anticipate a certain taste, you may be surprised at what happens:

https://www.quantamagazine.org/brains-speed-up-perception-by-guessing-whats-next-20190502/

"Imagine picking up a glass of what you think is apple juice, only to take a sip and discover that it’s actually ginger ale. Even though you usually love the soda, this time it tastes terrible. That’s because context and internal states, including expectation, influence how all animals perceive and process sensory information, explained Alfredo Fontanini, a neurobiologist at Stony Brook University in New York. In this case, anticipating the wrong stimulus leads to a surprise, and a negative response.

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"Years ago, Fontanini and his team found direct neural evidence of this speedup effect in the gustatory cortex, the part of the brain responsible for taste perception. Since then, they have been trying to pin down the structure of the cortical circuitry that made their results possible. Now they have. Last month, they published their findings in Nature Neuroscience: a model of a network with a specific kind of architecture that not only provides new insights into how expectation works, but also delves into broader questions about how scientists should think about perception more generally. Moreover, it falls in step with a theory of decision making that suggests the brain really does leap to conclusions, rather than building up to them.

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" Currently, neuroscientists are debating how taste gets processed: Some argue that certain neurons might encode “sweet” and others “salty,” creating very specific neural signatures for specific tastes. Others tie it to broader patterns of activity; most neurons respond to most tastes, and a given neural signature is more roughly correlated with one taste over another. The work done by Fontanini and his colleagues supports the latter theory while providing predictions about what that connectivity should look like. The clusters alone “capture many, many features of the gustatory cortex,” Fontanini said: “the spontaneous activity, the patterns of response to taste, the expectation effect.”

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"The way experts think about basic sensory perception tends toward the hierarchical: The cortex builds up and integrates features to form perceptions, sending signals to other layers of the network that integrate still more information until the brain ultimately arrives at a decision or behavior.

"Not so in this new work. Instead, the team’s results support a different kind of processing in which “all of this happens at the same time, and … before the stimulus even arrives,” said Leslie Kay, a neuroscientist at the University of Chicago who focuses on olfaction. “You learn stuff within a cortical area,” forming a system of connected clusters to reflect that learning, “and then you influence it [with expectation], and what it knows emerges.”

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"It also highlights the need to move away from focusing on single neurons that respond to particular cues, and toward making internal states and dynamics more explicit in our understanding of sensory networks — even for the most basic sensory stimuli. “It’s much easier to say that a neuron increases its firing rate,” said Anan Moran, a neurobiologist at Tel Aviv University in Israel. But to understand how organisms work, “you cannot account only for the stimulus, but also for the internal state,” he added. “And this means that our previous [understanding of] the mechanism used by the brain to achieve perception and action and so on needs to be reevaluated.”

“'The stuff going on in the gustatory cortex before the stimulus arrives is a large part of how that stimulus gets processed when it gets there,” Katz said. And in this case, examining how those internal states get modified by an experience or cue revealed something about the overall network connectivity."

Comment: This does not show that the brain is in charge of us. It shows that the brain sets up networks to help us by anticipating the next step in the sensory process. This is built into the brain's designed activity.