Measuring N170 Potential using Gaming EEG System

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COGS lab report 1

Psychology (Macquarie University)

StuDocu is not sponsored or endorsed by any college or university

COGS lab report 1

Psychology (Macquarie University)

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EEG experiment

Introduction

The human brain is an extraordinary organ that contributes to all aspects of human

functioning and many specific areas control different emotions, actions and memory.

In this experiment the N170, an event-related potential (ERP), reveals significant

response in neural activity to the recognition of faces. This experiment also conducted

by De Lissa, Sorenson, Badcock and Thie, (2015) contribute to the verification of the

role of N170 in the perception of faces. The testing hypothesis was that the N170 is

larger in response to faces than other objects. This was tested against the identification

of watches both inverted and upright contributing to the validity of the hypothesis.

The second hypothesis tested was that N170 is sensitive to face inversion resulting in

delays in the onset of the N170. Inverted and upright faces were used to test axonal

performance. The dependent variables that were measured included the amplitude of

the potential in N170 and its latency. The independent variable that was manipulated

was the stimuli of upright and inverting of faces and watches.

Method

One student participant had the role of wearing the electrode cap, using their brain

recordings to test the ERP. The EEG electrode cap was connected to the EEG system

that presented results of the stimuli on the desktop via TestBench software. This event

marking system was added to the commercial gaming emotive epoc, significant for

the detection of axonal responses. 16 electrodes in the cap had dental rolls soaked in

saline solution and placed between the electrodes and the participant’s scalp. The

electrodes situated on the mastoid bones were considered as reference electrodes and

these were important for testing impedance. Once all electrodes indicated green on

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TestBench, the experiment began by revealing upright and inverted faces and

watches, randomly. In total, 300 images were shown. The participant’s job was to

press F for face and W for watch on the keyboard whenever the corresponding image

was shown on the screen. The EEG signal for the participant’s brain activity was then

recorded. This experiment was conducted three times.

Results

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Graph 1 reveals the reaction reached N170 when stimulated by images of faces

whereas it didn’t in response to watches. The red line indicated this.

Graph 2 depicts the difference in brain activity when stimulated by inverted and

upright faces. The red line demonstrates that inverted faces delayed in reaching N170

than the reaction for upright faces.

Discussion

The significance of the findings in this experiment validates the hypothesis that the

N170 is relational with facial recognition. The axonal response to detecting faces

shows large potential concluding that this part of the brain is responsible for

identification of faces in comparison to watches, recognizing that the N170 is not

powered by complexity. Correspondingly, as both tasks for identifying watches and

faces were the same, this concludes that the N170 is also not powered by task

demands. The N170 response was also delayed for inverted faces, supporting the

hypothesis of the experiment. The amplitude of the N170 for both upright and

inverted faces were similar, elucidating that facial recognition is disrupted by

inversion. This may however indicate that the N170 is involved in developing face

structure and not recognition. As a result, the experiment’s validity was contributed

by performing the task three times and replicated by numerous scientists who also

demonstrate the same results. In spite of that, in order to further verify the results,

subjects placed in a quiet room with no distraction could have assisted with the

amount of talk or movement that hindered the findings. Other limitations of the

findings are that the EEG is correlational and not causal.

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References

De Lissa, Peter, Sörensen, Sidsel, Badcock, Nicholas, Thie, Johnson, McArthur,

Genevieve, & Macquarie University. Department of Cognitive Science.

(2015). Measuring the face-sensitive N170 with a gaming EEG system : A

validation study.

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