Measuring N170 Potential using Gaming EEG System

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COGS 100 Lab 1 - SAMPLE LAB REPORT

Cognitive Sciences (Macquarie University)

StuDocu is not sponsored or endorsed by any college or university

COGS 100 Lab 1 - SAMPLE LAB REPORT

Cognitive Sciences (Macquarie University)

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COGS100 Lab-report 1

Measuring N170’Potential Via Gaming

EEG System Jason He (45182043)

1. Introduction

The N170 is a face sensitive even-related potential (ERP) that occurs over the occipito-temporal

region of the brain at around 170-ms. N170’s not only gives larger response to faces than to objects

but is also sensitive to face inversion, N170 onset is delayed significantly when face in inverted

(DeLissa et al, 2015). It is hypothesized that:

1.N170 is larger in response to faces than to other objects.

 H0 (null hypothesis): N170 response to faces and objects is the same.

 H1(alt hypothesis): N170 response to faces is larger than the N170 response to objects.

2.N170 is sensitive to face inversion, which delays N170 onset.

 H0 (null hypothesis): N170 onset is not sensitive to face inversion, which does not delay

N170 onset.

 H1(alt hypothesis): N170 response to inverted faces is delayed.

Independent variables: upright or inverted images of human faces or watches.

Dependent variables: N170 size (=amplitude)

N170 time (=latency)

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2. Methods:

Three Cognitive and brain science undergraduates undertook the experiment. One being the

experimental subject and two records relevant details during the process of the experiment.

2.1. Experiment set up

Multiple cylinder-shaped cotton balls are soaked in saline solution. The soaked cotton balls are

then inserted into the electrodes of EPOC headset which was later put on the participant’s head.

The headset is connected to a desktop and data was recorded via TestBench software.

2.2 Stimuli

Participant was asked to sit in front of the desktop as stimuli were presented on the desktop. The

stimuli were 30 upright and inverted images of human faces and wrist watches. The stimulus began

with a 500-ms black background that had a fixation cross in the center. Then it immediately

changed to a 200-ms upright or inverted image of face or watch followed by black screen until

response, the participant was asked to indicate whether the image was upright or inverted by

clicking 2 different keys on the keyboard. After response, a 2000-ms ‘blink’ screen came up before

the commencement of a new trial.

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3. Results

Figure 1 compares the waveforms generated by N170 ERP when stimulated by images of

upright faces or upright watches. As illustrated, at around 200-ms, the waveforms generated by

faces (Red) is significantly larger than to watches as it has a larger amplitude. N170 had an active

response to upright faces but passive response to watches.

Figure 2 compares the waveforms generated by N170 when stimulated by images of inverted

faces or watches. In comparison to figure 1, in figure 2, the N170 response is slightly delayed when

exposed to inverted face, however the waveform produced by inverted faces is still larger than

inverted watches.

4.Discussion

In sum, the results indicate that the N170 ERP exhibits sensitivity to face than to objects

(DeLissa et al, 2015). Mean amplitude and peak amplitude of the waveforms generated by face

stimuli is larger than to watches stimuli. Also, N170 onset is delayed in response to inverted faces.

These results successfully demonstrated the two key effects of the N170. It has proved the

reliability of the EPOC EEG system and support the use of such inexpensive system as an

alternative to research-grade system for studies in face processing (DeLissa et al, 2015). Potential

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Faces

Figure 2Figure 1

Amplitude (V)Amplitude (V)

Latency (m/s)

Latency (m/s)

Watches

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limitations of this study could be the placement of the electrodes, electrodes might not be placed in

desired locations for indexing N170 due to humanly operations to the headset. To prevent such

error, future experiments would benefit from having a more structured electrode placement for the

EPOC headset to prevent undesired electrode movement.

References:

Badcock, N., De Lissa, P., McArthur, G,. Sorensen, S., Thie, J. (2015). Measuring the face-

sensitive N170 with a gaming EEG system: A validation study. Journal of Neuroscience Methods,

253 (2015), 47–54. doi: http://dx.doi.org/10.1016/j.jneumeth.2015.05.025

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