Persistence and accommodation in short-term priming and other perceptual paradigms: temporal segregation through synaptic depression

Abstract

Perceptual input changes constantly in an unpredictable fashion, often changing before our somewhat sluggish perceptual systems have adequately processed this input. This can give rise to source confusion-how do we know whether a given perceptual activation is due to the current input, or a previous input that had yet to be completely processed? We propose that activity-dependent neural accommodation naturally limits this source confusion by suppressing items once they have been identified. We review behavioral paradigms from different literatures that measure the correlates of persistence and accommodation. Of the various accommodative mechanisms, we focus on synaptic depression, deriving a rate-coded expression that can be used to produce accommodating dynamics in any neural network with real valued activation. We implement this expression in a hierarchical model of perception termed, "a neural mechanism for responding optimally with unknown sources of evidence" (nROUSE). This model can be viewed as a more detailed version of the more abstract ROUSE model of Huber, Shiffrin, Lyle, and Ruys (2001), which produces accommodated levels of feature evidence through an optimal calculation. We apply nROUSE to three short-term priming experiments that manipulated prime duration.

A habituation account of change detection in same/different judgments

“…Building on a theory of short-term priming (Huber & O'Reilly, 2003; see also Huber, 2008b), we favor the view that the perceptual system primarily employs mechanisms for detecting differences between stimuli rather than similarities. This theory explained a series of experiments (Huber, Shiffrin, Lyle & Quach, 2002a;Huber, Shiffrin, Lyle, & Ruys, 2001;Huber, Shiffrin, Quach, & Lyle, 2002) that used a two-alternative forced choice (2AFC) paradigm in which a briefly flashed (and masked) target stimulus needed to be identified.…”

“…As reviewed in Huber (2008b), this pattern of results is readily explained by proposing that the perceptual system habituates to any stimulus attended (e.g., a prime) and that the amount of habituation becomes greater with longer prime durations (Huber, 2008b;Huber & O'Reilly, 2003). According to this theory, when a prime is very salient, the primed choice word (target or foil) is still in a habituated state when the choice words appear, slowing down perceptual processing for that choice.…”

“…This theory was first instantiated as a formal model called "Responding Optimally with Unknown Sources of Evidence" (ROUSE; Huber et al, 2001). We focus on the neurocomputational version of ROUSE (nROUSE; Huber & O'Reilly, 2003), which is a neural model for novelty detection. This neural model produces habituation through "synaptic depression," as we explain next.…”

“…In most neurocomputational models of cognitive processes, the activation of internal representations increases with increasing stimulus duration (but see Gotts &Plaut, 2002, andO'Reilly, 2003). However, these models are at odds with the common observation that neuronal firing rates change nonmonotonically with changes in the duration of relevant stimuli (Tsodyks & Markram, 1997).…”

“…Using a model of habituation through synaptic depression, Huber and O'Reilly (2003) showed that for the short-term priming paradigm, the time needed to achieve peak activation for each choice (i.e., perceptual fluency) captured both positive priming following short prime durations and negative priming following long prime durations. Similar to the interactive-activation model of McClelland and Rumelhart (1981), this was done with a three-layer (visual, orthographic, and lexical-semantic) network, although the representations at each layer were localist, and synaptic depression was used for all simulated neurons.…”