Stimulus-specific Cortical Visual Evoked Potential Morphological Patterns

Summary

In this paper, we present a protocol to investigate differential cortical visual evoked potential morphological patterns through stimulation of ventral and dorsal networks using high-density EEG. Visual object and motion stimulus paradigms, with and without temporal jitter, are described. Visual evoked potential morphological analyses are also outlined.  

Abstract

This paper presents a methodology for the recording and analysis of cortical visual evoked potentials (CVEPs) in response to various visual stimuli using 128-channel high-density electroencephalography (EEG). The specific aim of the described stimuli and analyses is to examine whether it is feasible to replicate previously reported CVEP morphological patterns elicited by an apparent motion stimulus, designed to simultaneously stimulate both ventral and dorsal central visual networks, using object and motion stimuli designed to separately stimulate ventral and dorsal visual cortical networks.  Four visual paradigms are presented: 1. Randomized visual objects with consistent temporal presentation. 2. Randomized visual objects with inconsistent temporal presentation (or jitter).  3. Visual motion via a radial field of coherent central dot motion without jitter.  4. Visual motion via a radial field of coherent central dot motion with jitter.  These four paradigms are presented in a pseudo-randomized order for each participant.  Jitter is introduced in order to view how possible anticipatory-related effects may affect the morphology of the object-onset and motion-onset CVEP response.  EEG data analyses are described in detail, including steps of data exportation from and importation to signal processing platforms, bad channel identification and removal, artifact rejection, averaging, and categorization of average CVEP morphological pattern type based upon latency ranges of component peaks. Representative data show that the methodological approach is indeed sensitive in eliciting differential object-onset and motion-onset CVEP morphological patterns and may, therefore, be useful in addressing the larger research aim. Given the high temporal resolution of EEG and the possible application of high-density EEG in source localization analyses, this protocol is ideal for the investigation of distinct CVEP morphological patterns and the underlying neural mechanisms which generate these differential responses.      

Introduction

Electroencephalography (EEG) is a tool that offers an inexpensive and non-invasive approach to the study of cortical processing, especially when compared to cortical assessment methods such as functional magnetic resonance imaging (fMRI), positron emission tomography (PET), and diffusion tensor imaging (DTI)¹. EEG also provides high temporal resolution, which is not possible to attain when using measures such as fMRI, PET, or DTI². High temporal resolution is critical when examining central temporal function in order to obtain millisecond-precision of neurophysiologic mechanisms related to the processing of specific inpu....

Protocol

All methods described here have been approved by the Institutional Review Board (IRB) for Human Research at the University of Texas at Austin.

1. Stimuli Characteristics

1. Create object stimuli using open source images available through the Bank of Standardized Stimuli (BOSS). This database consists of standardized images used throughout visual cognitive experiments.  Download four images (e.g., ball02, book01a, brick, button03) with a high rate of identification (above 75%)^20,21.  
2. Create motion stimuli using a modified version of the DotD....

Results

Figure 3 and Figure 4 show the representative object-onset and motion-onset CVEP results of five participants, aged 19-24 years, who passively viewed each visual paradigm. This design allowed observation of CVEP responses elicited by visual objects (with and without jitter) and visual motion (with and without jitter) both within and across subjects according to each condition.  Participant CVEPs were grouped according to the morphological pattern elicited b.......

Discussion

The goal of this methodological report was to evaluate the feasibility in recording differential CVEP morphology by using visual object and motion stimuli specifically designed to separately stimulate ventral and dorsal streams in passive viewing tasks^6,7,8, both with and without variation of ISIs (jitter)¹⁹. Conditions were not designed to be directly compared, rather, observations were made as to whethe.......

Materials

Name	Company	Catalog Number	Comments
E-Prime 2.0	Psychology Software Tools, Inc		Used in data acquisition
Net Amps 400	Electrical Geodesics, Inc		Used in data acquisition
Net Station Acquisition V5.2.0.2	Electrical Geodesics, Inc		Used in data acqusition
iMac (27-inch)	Apple		Used in data acquisition
Optiplex 7020 Computer	Dell		Stimulus computer
HydroCel GSN EEG net	Electrical Geodesics, Inc		Used in data acqusition
1 ml pipette	Electrical Geodesics, Inc		Used to lower impedances
Johnson's Baby Shampoo	Johnson & Johnson		Used in impedance solution
Potassium Chloride (dry)	Electrical Geodesics, Inc		Used in impedance solution
Control III Disinfectant Germicide	Control III		Used in disinfectant solution
32-inch LCD monitor	Vizio		Used to present stimuli
Matlab (R2016b)	MathWorks		Used in data analysis
EEGlab v14.1.2	Swartz Center for Computational Neuroscience, University of California, San Diego	https://sccn.ucsd.edu/eeglab/index.php	Used in data analysis
BOSS Database	Bank of Standardized Stimuli	https://sites.google.com/site/bosstimuli/	Used in generation of visual object stimuli
Psychtoolbox-3	Psychophysics Toolbox Version 3 (PTB-3)	http://psychtoolbox.org/	Used in generation of visual motion stimuli