Zero Brane

Studies of Goal Directed Movements

Sun, 13 Aug 2006 21:40:59 GMT

Studies of Goal Directed Movements by Emanuel V. Todorov

The main idea [of the discussion on a Bayesian model of sensory-motor processing] was that the sensory-motor system uses a casual model to predict the outcomes of hypothetical actions, and a generative model to predict sensory stimuli arising from hypothetical states of the world. These two models are then "inverted" via some powerful computation. [The Kalman filtering algorithm] does exactly that: the first line is the casual model describing the hand dynamics, and the second line is the generative model describing how sensory inputs arise. (p. 29)

Motor templates and learning

Memory decay and target resampling

Imagine that for some reason the controller is using inaccurate estimates of the noise terms in the system. In particular it is too confident in the sensory input (G is smaller than the actual amount of sensory noise) and too skeptical about stability of the world (D is larger than the actual amount of additive system noise). Such a controller will use a Kalman gain K larger than the optimal value i.e. it will overcorrect based on sensory inputs; in particular, in the absence of inputs the gain will not become exactly 0 and thus the state estimate (memory) will gradually degrade. Furthermore, the estimated variance of the state will be larger than its true value, thus from the point of view of the controller it will be advantageous to sample the sensory input as often as possible, and in particular look at the targets even if they have been presented before the movement. (pp. 38-9)

Sensory adaptations

Using a default control law L that corrects for systematic perturbations detected on previous trials can have effects quite similar to sensory adaptations. (p. 39)

It is possible that the primary objective of the adaptation process is restoring performance of the task (i.e. acquire the target withing the time limit) rather than restoring the shape of the baseline trajectory -- the latter being an epiphenomenon. (p. 93)

The Feeling of What Happens

Fri, 05 May 2006 05:11:31 GMT

The Feeling of What Happens
by Antonio Damasio

Emotion and Consciousness

Fri, 05 May 2006 04:59:59 GMT

Emotion and Consciousness: End of a continuum
Yuri I. Alexandrov, Mikko E. Sams
Cognitive Brain Research 25 (2005) 387-405

Metamagical Themas

Sat, 29 Apr 2006 05:06:31 GMT

Metamagical Themas: Questing for the Essence of Mind and Pattern
by Douglas R. Hofstadter

The Quest for Consciousness

Sat, 22 Apr 2006 04:35:35 GMT

The Quest for Consciousness: A Neurobiological Approach
by Christof Koch

Fluid Concepts and Creative Analogies

Fri, 21 Apr 2006 04:21:45 GMT

Fluid Concepts and Creative Analogies: Computer Models of the Fundamental Mechanisms of Thought
by Douglas R. Hofstadter

The Magical Number Seven, Plus ot Minus Two

Wed, 29 Mar 2006 06:58:59 GMT

The Magical Number Seven, Plus ot Minus Two: Some Limits on Our Capacity for Processing Information
by George A. Miller

There is a clear and definite limit to the accuracy with which we can identify absolutely the magnitude of a unidimensional stimulus variable. I would propose to call this limit the span of absolute judgment, and I maintain that for unidimensional judgments this span is usually somewhere in the neighborhood of seven. We are not completely at the mercy of this limited span, however, because we have a variety of techniques for getting around it and increasing the accuracy of our judgments. The three most important of these devices are (a) to make relative rather than absolute judgments; or, if that is not possible, (b) to increase the number of dimensions along which the stimuli can differ; or © to arrange the task in such a way that we make a sequence of several absolute judgments in a row.

I suspect that there is also a span of perceptual dimensionality and that this span is somewhere in the neighborhood of ten, but I must add at once that there is no objective evidence to support this suspicion.

...there is a finite span of immediate memory and that for a lot of different kinds of test materials this span is about seven items in length. Absolute judgment is limited by the amount of information. Immediate memory is limited by the number of items. In order to capture this distinction in somewhat picturesque terms, I have fallen into the custom of distinguishing between bits of information and chunks of information. The span of immediate memory seems to be almost independent of the number of bits per chunk, at least over the range that has been examined to date. The contrast of the terms bit and chunk also serves to highlight the fact that we are not very definite about what constitutes a chunk of information.

Cognition and Reality

Wed, 29 Mar 2006 06:29:07 GMT

Cognition and Reality: Principles and Implications of Cognitive Psychology
by Ulric Neisser

Banishing the Homunculus

Mon, 13 Mar 2006 05:50:56 GMT

Banishing the Homunculus: Making Working Memory Work
Hazy, T.E., Frank, M.J. & O'Reilly, R.C. (2006)
Neuroscience.

An important paper that outlines six key functional demands underlying working memory and presents a working memory model based on representations in the prefrontal cortex which are dynamically gated by the basal ganglia (PBWM). Working memory is described as controlled activation of stable configurations that exist throughout the cortex (rather than a separate module with information being moved between long-term memory and working memory bufers).