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Voluntary attention modulates fMRI activity in human MT-MST

Voluntary attention modulates fMRI activity in human MT-MST. O’Craven , K. M., Rosen, B. R., Kwong , K. K., Treisman , A. and Savoy, R. L. (1997) Neuron , 18 , 591-598. Take home massage. Voluntary attention can influence the neural activity of the MT-MST complex. Introduction.

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Voluntary attention modulates fMRI activity in human MT-MST

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  1. Voluntary attention modulates fMRI activity in human MT-MST O’Craven, K. M., Rosen, B. R., Kwong, K. K., Treisman, A. and Savoy, R. L. (1997) Neuron, 18, 591-598.

  2. Take home massage • Voluntary attention can influence the neural activity of the MT-MST complex.

  3. Introduction • MT-MST complex (V5) is a region of human visual cortex that is specialized for the processing of visual motion. • Neurons in V5 are mostly tuned to direction of motion, and are activated when a large visual scene contains motion. • The response properties of MT and MST have been well studied in monkeys. • In human?...

  4. Introduction A small part of Brodmann’s area 37 and largely coincident with Flechsig’s field 16

  5. Microelectrode recordings in monkey • Attention can modulate the responses of individual neurons in visual cortex. • Attention can cause changes in receptive field size and in the tuning curves for color, orientation, and direction selectivity. • Now with fMRI on human?...

  6. Question • Whether voluntary attention can modulate neural activity in the human cortical areas responsible for processing simple visual motion information? • If visual stimulus remains unchanged  can neural activity of visual area based solely on the attended subset of the stimulus? • In this case, including moving and stationary stimulus subsets

  7. Experiment • 2 Experiments: • Experiment 1 fixed stimulus demonstrate the effect of attentional change • Experiment 2 more complex stimulus paradigm quantitative comparisons between stimulus-driven and attention-driven modulation of activity

  8. Experiment • 2 Experiments: • Experiment 1 fixed stimulus demonstrate the effect of attentional change • Experiment 2 more complex stimulus paradigm quantitative comparisons between stimulus-driven and attention-driven modulation of activity

  9. Experiment 1 • 3 participants • Verbal cue to alert the subject to which color of dots • Scan time: 220 s • Attention altered every 20 s • The motion distinction was never mentioned to participants

  10. Experiment 1 -- result • 3 participants’ data were averaged • 1C: attend to moving white dots v.s. attend to stationary black dots • The difference is purely attentional effect (identical stimulus through run) • The location is consistent with the location of human MT in other studies • Attention modulates activation in the MT-MST complex

  11. Experiment • 2 Experiments: • Experiment 1 fixed stimulus demonstrate the effect of attentional change • Experiment 2 more complex stimulus paradigm quantitative comparisons between stimulus-driven and attention-driven modulation of activity

  12. Experiment 2 • 5 participants • 6 runs each with 4 epochs • Attention: 3 run to black/white • “Castle” paradigm (O’Craven) • 20 s each block • Attend to moving dots in the 1st, 3rd epoch • Additional baseline:20 s with no dots

  13. Experiment 2 -- result • 5 participants’ data were averaged over 6 runs • 2B: localization of MT is where the activation were more active during motion stimulus than during stationary stimulus.(independent of attention) • Attention to the moving dots clearly increased the activation (29%, but significant) elicited by the mixed stimulus. • Voluntary attention modulates activation in the MT-MST complex

  14. Experiment 2 -- result • The result of the time course were consistent across subjects • The V1 and V2 activity differences did not associated with the attentional task. • It was not observed in this study, but might be discovered when using different task.

  15. Discussion • Eye movement: • No noticeable differences between conditions • No significant eye blink frequency difference between conditions • The result was not produced by eye movement

  16. Conclusion & Discussion • Voluntary attention to different elements in a single visual display can affect neural activity in areas of visual cortex responsible for basic sensory processing of visual information. • The “late selection” view v.s. the “early selection” view of attention  the level depends on the task and the load • This study offers a clear example of early selection by top-down control of sensory processing

  17. Conclusion & Discussion • This study agrees with other experiments that include stimulus changes or task changes between condition during experiment. • The result cannot be taken as conclusive evidence regarding object-based attention, but it is nonetheless suggestive. • Attention can affect cortical processing throughout the human brain.

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