The Behavioral and Electrophysiological Effects of Discrimination and Inhibition Training on Visual Selective Attention: an ERP and Time-Frequency Analysis

Enhancement of task relevant information and the suppression of task irrelevant information are the two co-occurring mechanisms of selective attention. Studies have shown that ERP components (specifically N2, P3, and RP) and the alpha band (8-14 Hz) rhythm correspond to neural mechanisms and processes of visual selective attention, especially conflict resolution. Tested by a modified version of the visual flanker task, a conflict task employing inhibitory control, two groups of healthy adults were exposed to three weeks of cognitive training; either discrimination training (trained to discriminate target orientation) or inhibition training (trained to ignore interfering distractors) to investigate whether training impacts behavioral and neural correlates associated with stimuli processing. Behavioral analysis revealed a reduction in both Garner interference [F(1,33)=6.85, p=0.01] and Congruity effect [F(2,66)= 4.35, p=. 02] after inhibition training, indicating better conflict resolution. Neural analyses revealed that the amplitude of N2 to target stimuli increased equally for both congruent and incongruent trials, albeit to a larger degree after inhibition training compared to discrimination training [F(1,32)= 5.18, p<. 05]. Meanwhile, inhibition training decreased the magnitude of P3 [F(1,32)= 5.69, p<. 05] and increased the magnitude of Rejection Positivity (RP) [F(1,32)= 4.87, p<. 05] to incongruent distractors. As the magnitude of RP increased, behavioral performance (RT and accuracy) improved across both training groups. As the first alpha-band training study, we found non-group specific training effects which did not vary as a function of either discrimination training or inhibition training. Hence, we suggest that the alpha band may not be amenable to inhibitory control training employing a conflict task. Instead, the training effects are specific to the ERP waveforms: N2, P3, and RP. TRAINING EFFECTS ON VISUAL SELECTIVE ATTENTION 3 The Behavioral and Electrophysiological Effects of Discrimination and Inhibition Training on Visual Selective Attention: an ERP and Time-Frequency Analysis One of the most fundamental executive functions in humans is our use of attention to prioritize information, which lays the groundwork for all our understanding, learning, and innovating. It is understood that attention is a cognitive resource that is limited in the amount available to allocate, making it imperative that one uses the limited attention available appropriately and optimally. Being constantly surrounded by numerous stimuli begging for one’s attention, individuals must be able to filter the relevant information from the irrelevant information (Lavie, Hirst, de Fockert, & Viding, 2004). An individual’s ability to focus on relevant information (e.g. targets) presented in the environment, while ignoring the irrelevant information (e.g. distractors), is defined as selective attention (Melara, Rao, & Tong, 2002; Paczynski, Burton, & Jha, 2015; Feldmann‐Wüstefeld, Uengoer, & Schubö, 2015; Schneider, 2017; Moore & Zirnsak, 2017). How the relevant information is selected and filtered from the abundance of stimuli in the environment in the process of selective attention has been heavily debated and researched over the years. In the recent years, researchers have strived to train participants in selective attention capabilities by trying to improve components of selective attention such as inhibitory control (Melara et al., 2002; Thorell et al., 2009; Berkman et al., 2014) or conflict resolution (Rueda et al., 2005; Millner et al., 2012). The efficient use of these components of selective attention is integral for an individual to make optimal use of their limited capacity. Contrary to the traditional view of selective attention which focuses on target processing, these components of selective attention pertain to the processing of distracting and interfering information as an individual allocates his or her attention to the task at hand. Hence, training individuals to TRAINING EFFECTS ON VISUAL SELECTIVE ATTENTION 4 improve their attentional control by suppressing distractors using inhibitory control and conflict resolution is the next step in increasing our understanding of the mechanisms of selective attention. Moreover, the current study extended previous research on selective attention by demonstrating that inhibitory control is amenable to training in the visual modality and is associated with improved attentional capabilities under conflict and non-conflict situations. Traditional Theories of Selective Attention The traditional theories of selective attention, proposed by Broadbent (1958), Deutsch and Deutsch (1963), and Treisman (1964), characterized selective attention mechanisms as corresponding primarily to the activation of target processing. Theories of selective attention sought to understand how perceived information is selected and processed. Broadbent (1958) proposed that because it is impossible for all incoming stimuli to be processed, attention is limited in capacity, hence, a “bottleneck” filter must be in place that limits the flow of information from the environment. The bottleneck model postulates that salient information is filtered through to consciousness whereas the rest of the information is withheld from processing. How the salient information is detected, filtered, and processed was addressed by Broadbent (1958). He conducted an experiment using a dichotic listening task in which participants heard two differing messages in either ear; participants were instructed to repeat the messages heard in one ear (e.g. attended stimuli) while ignoring the messages from the other ear (unattended stimuli), a task called shadowing. Broadbent found that participants were able to successfully repeat the attended messages without excessive interference from the unattended messages. Broadbent (1958) proposed his Filter theory (now called the Early Selection Theory of Attention), which stated that all incoming stimuli enter through a sensory buffer from which the relevant information is filtered out from the irrelevant information, based primarily on the TRAINING EFFECTS ON VISUAL SELECTIVE ATTENTION 5 physical characteristics of the stimuli. In this account, only relevant information is filtered through and processed for meaning, whereas other irrelevant information is filtered out and lost. Although the theory captures many everyday examples of selective attention, phenomena such as the cocktail party effect cannot be explained using this theory. The cocktail party effect occurs when an individual is able to hear his or her own name even when engaged in another task or conversation, suggesting that unattended information is not filtered out completely or lost from processing (Cherry, 1953). Addressing this discrepancy, researchers Deutsch and Deutsch (1963) proposed an alternative model from the Filter theory which stated that all incoming information is processed for meaning prior to the filtering out of the irrelevant information (now called the Late Selection Theory of Attention). This model suggests that all stimuli registered by the senses is defined for meaning subconsciously from which the unattended information is filtered out and the attended information reaches conscious awareness for full processing. Therefore, any pertinent information embedded in the unattended channel is perceived because the unattended stimuli are processed for meaning, thus explaining the cocktail party phenomenon. To Treisman (1964), who agreed with Broadbent (1958) in early selection, the processing for meaning of all incoming stimuli appeared to be a wasteful use of cognitive resources, hence he suggested the attenuation of unattended information rather than the complete filtering out prior to semantic processing. Treisman (1964) proposed that all the relevant incoming information reaches semantic processing while the irrelevant information is attenuated, reduced in intensity, such that it is not completely processed, yet it is not fully ignored either. Treisman (1964) reproduced Broadbent’s (1958) experiment using a dichotic listening task and a shadowing method to show that unattended messages are not completely ignored because if the unattended stream contains TRAINING EFFECTS ON VISUAL SELECTIVE ATTENTION 6 relevant information (e.g. the participant’s name), they will be processed. Treisman’s theory (now termed the Attenuation Theory of Attention) addresses both the Early and Late Selection Theories and suggests an intermediate position for the mechanism of selective attention in which the attended information is fully processed for meaning, whereas the unattended information is passively processed because the “attenuator” reduces the intensity of the unattended incoming stimuli, but does not inhibit processing completely. This process allows us to pay attention to relevant information in our environment while being passively aware of other unattended stimuli.