Presentation 2

Question 1

Slide 1: Intro

Answer 1

My name is Gitanjali Sharma and today I will be doing a presentation on a paper called the Spatial-Temporal Analysis of Feature-Based Attention by Schoenfeld et al., (2007)

Question 2

Slide 2 - what is feature-based attention? - (2)

Answer 2

• Objects are generally defined by their collection of the features they have
• Feature-based attention involves selectively attending to features of a visual stimulus such as their colour, brightness, motion, size or shape.

Question 3

Slide 2 - what was the aim of the study?

Answer 3

• The aim of Schoenfeld et al’s study was to combine both event-related potentials (EEG) and event-related fields ( ;MEG) with recordings from fMRI to investigate the neural correlates as well as the time course of feature-based attention.

Question 4

Slide 2 - what was the procedure of the study? - (11)

Answer 4

• The procedure for this study is seen in figure below in which…:
• • In each blocks of the experimental trials began with a cue indicating the stimulus feature to be attended which was motion (M) or colour (C).
• The dots were stationery in the interstimulus interval and then dots would move to the right or would change colour for 300ms.
• The motion and colour stimuli were presented in a random order in the experiment
• For each feature, there were 2 alternate stimuli:
• For motion stimuli, the dots either fast or slow moving to the right
• For colour stimuli, the dots either had a red or orange colour change.
• Pps were instructed in the experiment to press a button as quickly as possible upon detecting fast motion when motion was attended feature or the orange colour change when colour was attended feature.
• They compared the participants’ response to movement trials when motion was attended and unattended
• They also compared participants’ responses to colour trials when colour was attended and unattended
• There was 4 stimulus conditions x 2 attention conditions so 8 different experimental conditions altogether .

Question 5

Slide 3 - fMRI results - (3)

Answer 5

• The results from the fMRI recordings show that attending to colour increased the activity in V4 (in the posterior fusiform gyrus) as compared to not attending to colour
• Attending to motion increased activity in V5 as compared to not attending
• These activations of V4 and V5 were bilateral so happening on both sides of the hemispheres of the brain (point to the screen)

Question 6

Slide 4 - EEG MEG Results - (3)

Answer 6

• The results from the event-related potentials as well as event-related fields from EEG and MEG showed that:
• The difference between the attending to motion (red) vs unattending (blue) was significant at approximately 110 to 120 milliseconds- point to screen
• Additionally, the difference between attending to colour (Red) vs unattending (blue) waveforms was significantly at approximately the time range of 90 to 110 milliseconds = point to screen

Question 7

Slide 5 - Conclusion - (5)

Answer 7

• In conclusion, this study provides evidence for the neural correlates of feature-based attention
• The study showed that attention to features leads to an increased response in its expected and relevant regions (motion its MT or V5 and colour its V4)
• They also used EEG/MEG to provide temporal information (when activation is happening)
• In this study, they found selectively attending to motion and colour began early (around 100 ms after stimulis onset), other studies showed that spatial attention (attending to a stimuli at a specific location) begins even earlier around 70 milliseconds after stimulus onset.
• Overall it shows that there are different underlying processes involved in spatial and feature based attention.