Varieties of neural activity

Here is a characteristic of human cortical dendrites that has not been found in mouse models:

“In contrast to typical all-or-none action potentials, dCaAPs were graded; their amplitudes were maximal for threshold-level stimuli but dampened for stronger stimuli. These dCaAPs enabled the dendrites of individual human neocortical pyramidal neurons to classify linearly nonseparable inputs—a computation conventionally thought to require multilayered networks.”

Albert Gidon1, Timothy Adam Zolnik1, Pawel Fidzinski, Felix Bolduan, Athanasia Papoutsi, Panayiota Poirazi, Martin Holtkamp, Imre Vida, Matthew Evan Larkum (2020) Dendritic action potentials and computation in human layer 2/3 cortical neurons. Science 03 Jan 2020: Vol. 367, Issue 6473, pp. 83-87. DOI: 10.1126/science.aax6239

Like all cells in a multicellular organism, nerve cells display two kinds of observable behavior.

From the cell’s point of view, the behaviors that matter to it are its means of controlling inputs that maintain its material integrity and its metabolic stability within its environment. We may observe consequent control of the stability of its environment; this includes collective control with other cells in its environment.

The behaviors that matter to the multicellular organism are necessarily neither perceived nor controlled as such by the cell, else conflict would arise between the two orders of control, the cellular level and the multicellular level. We as humans do not control variables that are vital to a nerve cell; the nerve cell does not control the rate of firing in its part of a control loop within a human nervous system. (The same principle applies to any hypothetical multi-body order of organisms in which individual humans participate, e.g. Kroeber’s notion of the ‘superorganic’.)

We must bear this distinction in mind as we learn more about the intra- and inter-cellular variables involved in neural activity. It is all relevant, but in different ways.

RM: Why do you think collective control is going on here? What is the evidence? What variables are the cells collectively controlling? How are they doing it? Is the collective control that is involved in cells’ behavior the same as the collective control that you say is involved in language behavior?

Best, Rick

14 posts were split to a new topic: Collective control, conflict, and stabilization

MT …the effects of all the dendrites working together coalesce at the soma of the neuron, maybe all having the same effect, maybe having balanced opposing effects. Either way, there is a collective effect of the dendritic operations on the soma, and at some point the soma fires a signal down its axon

RM: This is pretty much neurophysiology 101; the “collective” effects that multiple dendritic inputs, excitatory and inhibitory, can have on the firing rate of the axon leaving the soma are described in the Premises chapter of B:CP.

MT: What is “collective effect” as distinct from “collective control”? Consider the difference between side-effect and controlled effect of the output of a control loop on properties of the neighbouring environment… When, however, a lot of side-effects of different controlled perceptions affect the same environmental variable in the same direction, they have a collecttve effect on that variable.

RM: I think it’s clearer to say that a collective effect of the dendrites is their effect on the axon output, as shown in Figures 3.1-3.6 in B:CP. What you are describing as a “collective effect” is better described as a “collective side-effect” – a side-effect of the activity of a group of dendrites

MT: What I see in the small slice of Bruce’s message that you chose to quote is “collective effect”.

RM: But he wrote “collective control” instead, which is very different. I don’t have your ability to see what people really meant to write so I wish Bruce had cleared that up for me. But I still would like to know whether Bruce was referring to the well-known collective effect of dendrites on axon output or the collective side effect of dendritic activity on the substrate in which dendrites operate.

Best, Rick

Another variety of neural activity: Human hippocampal neurons track moments in a s

I don’t have access to the full article, but here’s what I can read:

Human hippocampal neurons track moments in a sequence of events

Leila Reddy, Benedikt Zoefel, Jessy K. Possel, Judith C. Peters, Doris Dijksterhuis, Marlene Poncet, Elisabeth C.W. van Straaten, Johannes C. Baayen, Sander Idema and Matthew W. Self


An indispensable feature of episodic memory is our ability to temporally piece together different elements of an experience into a coherent memory. Hippocampal “time cells” – neurons that represent temporal information – may play a critical role in this process. While these cells have been repeatedly found in rodents, it is still unclear to what extent similar temporal selectivity exists in the human hippocampus. Here we show that temporal context modulates the firing activity of human hippocampal neurons during structured temporal experiences. We recorded neuronal activity in the human brain while patients of either sex learned predictable sequences of pictures. We report that human time cells fire at successive moments in this task. Furthermore, time cells also signaled inherently changing temporal contexts during empty 10-second gap periods between trials, while participants waited for the task to resume. Finally, population activity allowed for decoding temporal epoch identity, both during sequence learning and during the gap periods. These findings suggest that human hippocampal neurons could play an essential role in temporally organizing distinct moments of an experience in episodic memory.

Significance Statement:

Episodic memory refers to our ability to remember the “what, where, and when” of a past experience. Representing time is an important component of this form of memory. Here, we show that neurons in the human hippocampus represent temporal information. This temporal signature was observed both when participants were actively engaged in a memory task, as well as during 10s-long gaps when they were asked to wait before performing the task. Furthermore, the activity of the population of hippocampal cells allowed for decoding one temporal epoch from another. These results suggest a robust representation of time in the human hippocampus.