Perception – Gain Control



Perception – Gain Control

|Task Name |Description |Cognitive Construct Validity |Neural Construct Validity |Reliability |Psychometric Characteristics |Animal Model |Stage of Research |

|Steady state visual |Magnocellular and parvocellular visual |The magnocellular-biased condition |The contrast response curves obtained in |There has been some work on |The task does not appear to |Single cell recordings from |There is evidence that this |

|evoked potentials to |pathway function assessed using |produces a steeply rising increase in |human studies in healthy controls (Butler |test retest reliability (Butler|have practice effects. It is a |magnocellular and parvocellular |specific task elicits deficits|

|magnocellular vs. |steady-state visual evoked potentials. |response to low contrast stimuli which |et al., 2001; Butler et al., 2005; Zemon &|et al., unpublished |passive viewing task in which |neurons in monkey lateral |in schizophrenia. |

|parvocellular biased |This task that takes ~ 15 min. The |reaches a saturation-level once luminance |Gordon, 2006) (Fox, Sato, & Daw, 1990) to |observations). Twenty |electrophysiological responses |geniculate nucleus (LGN) show | |

|stimuli. |magnocellular system responds to low |contrast reaches ~16% (Butler et al., |magnocellular- and parvocellular-biased |participants (10 controls and |are obtained. The responses do |characteristic |We need to assess psychometric|

| |luminance contrast and the parvocellular |2001; Butler et al., 2005; Zemon & Gordon,|stimuli are very similar to what is seen |10 schizophrenia patients) have|not habituate even following |electrophysiological responses. |characteristics such as |

| |system does not begin to respond until |2006). This leads to a characteristic |in single-cell recordings in monkeys |been tested twice. The |repeated presentation of the |Magnocellular neurons show steep|test-retest reliability, |

| |contrast has reached about 16%. In this |S-shaped, non-linear contrast gain control|supporting the concept that magnocellular |correlation between |stimulus conditions. It is not |increases in responding at low |practice effects, and |

| |task, isolated checks are modulated at low|curve. The initial steeply rising part of |and parvocellular responses are being |signal-to-noise ratios (the |a learned task, so that |contrast and saturation at |ceiling/floor effects for this|

| |contrasts to bias responding towards the |the curve reflects substantial |examined. In addition, visual pathways |dependent measure which is a |presentation at multiple test |higher contrast. Parvocellular |task. |

| |magnocellular visual pathway and are |amplification of low contrast stimuli, |within the brain use glutamate as their |measure of amplitude corrected |dates is not affected by prior |neurons show a shallow slope at | |

| |modulated around a high contrast |permitting M-pathway neurons to respond |primary neurotransmitter and NMDA appears |for noise) obtained in first |testing. There do not appear |low contrast and a |We need to study whether or |

| |"pedestal" to bias responding towards the |robustly even at low contrasts. This |to have a central role in gain control. |and second test sessions was |to be floor effects because |non-saturating response. The |not performance on this task |

| |parvocellular pathway. Signal-to-noise |magnocellular-pathway response is an |For instance, NMDA receptors amplify |significant (total group: |most people, including |curves found in the proposed |changes in response to |

| |ratio, which is the amplitude of the |example of gain control because response |responses to isolated stimuli as well as |r=0.81, p ................
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