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Cognitive Neuroscience (Fach) / Attention and Awareness (Lektion)
Attention and Awareness - done
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- Describe the Attention Experiment done by Herrmann von Helmholtz. He looked at a visual screen with rows of letters on it. During a trial he looked at the fixation cross in the middle. Then he illuminated the screen with brief flashes of light and found that he did hardly perceive the letters in the periphery of the screen. However, when he focused his attention on the upper right corner, he was able to perceive the letters easily. As a consequence, however, he did not perceive the letters in the non-attended quadrants. He concluded that there's a spotlight of attention: Only objects which are in the fcus of the attentional spotlight are perceived.
- Describe the Posner paradigm (covert spatial attention) and explain the supporting study. Participants fixate a cross on a computer screen during the entire trial. Left and right from the cross is a square. In either one the target may appear. Pps are asked to respond to the target as quickly as possible via button press. Before the target appears participants receive a cue (one of the squares turns red) as to where the target should be expected. The validity of the cue is varied (invalid cues: 20% of trials cue and target are in same location, neutral cues: 50% of trials cue and target in same location, valid cues: 80% of trials cue and target on same location). Response times are faster for valid cue trials.
- Explain endogenous and exogenous attention. How do both differ in the course of time in reference to target processing efficacy? Exogenous attention: Attention is guided externally, by buttom up cues (e.g. the cue appears at the site of target and automatically directs attention to that square). Endogenous attention: Attention is guided by the goals of the perceiver, top down (e.g. an arrow indicates where the target is likely to appear, but I still have to willingly direct my attention to that side). For exogenous attention target processing efficacy is highest at about 100ms after cue. After that target processing efficacy decreases rapidly, unless the direct cue is predicitve or interesting (in which case target processing efficacy stays high). For endogenous attention target processing efficacy increases much slower and is best after about 300ms and then stays as high.
- What is inhibition of return? Ward (2015): Attentional cues can facilitate or inhibit reaction to target. If the stimulus onset asynchrony between cue and target is longer than 200ms (graph) - 300ms (slide), the response to targets in cued locations are longer than compared to uncued targets. If the SOA is shorter cued targets are reacted to faster than uncued targets (facilitation).
- What is object based attention? Ward (2015): When two objects are in the same spatial location, we can focus our attention on either one object. This focus of attention has consequences for neuronal activity, When we attend to a face for example, then face-selective brain regions become more activated than when we attend to a house.
- Describe the attentional blink paradigm (Attention in the temporal Domain). Participants are presented with rapid serial visual stimuli on a screen (SOA: 100ms). They have to repond to certain targets (e.g. certain letters or numbers), with the first target being T1 and the second target being T2. The probability of getting T2 correct (given the reponse to T1 was correct) is measured. The time/frames in between both targets are varied. It can be found that T2 is detected worse 200-300ms after T1. This temporal reduction in awareness can be thought of as an attentional blink after T1.
- What is Feature Integration theory (FIT)? This theory way proposed by Treisman & Gelade (1980) and derived its evidence from visual search paradigms. FIT assumes that basic features are coded in parallel, allowing us to rapidly detect targets that do not share features with the other objects in a visual array. The target search time stays constant even when the numbe of distractors are varied, as the target "pops out". However, when the target can only be detected by a conjunction of features (e.g. color and shape, instead of color only), a serial search is necessary (the attentional "spotlight" inspects each object serially). Thus, target search time increases with increasing number of distractors.
- Explain the biased competition model. What evidence from neglect patients supports the model? Proposed by Desimone & Duncan (1995). Relies on evidence from neuroscience. Multiple stimuli compete for representation in visual cortex. This process is influenced by Top-down feedback mechanisms (fronto-parietal attentional network) and bottom-up sensory-driven mechanisms. Output to: Memory and motor systems. Neglect: Neglect patients fail to notice the stimulus on neglected side when two stimuli are briefly shown (in both sides). However, they notice stimulus on neglected side when it is shown in isolation. This suggests that attention depends on competition between stimuli.
- Explain the premotor theory of attention. Rizolatti et al. (1987, 1994): The premotor theory of attention proposes that orienting of attention is related to preperation of motor actions. This applies to overt and covert attention (covert attention is assumed to reflect movement that is planned but not executed). Study: Pps look at screen with four numbered squares in a row on top. In each trial a digit appears in an additional square in the center of the screen. The digit indicates where the target simulus is likely to appear (80% certainty). When the target appears in an unattended location, participants are faster at shifting attention to a location that requires a movement in the same direction as the planned movement to the cued location (compared to a target location that is equidistant but in the opposite direction).
- Describe the dorsal attention network and the ventral attention network (task, regions involved). Dorsal attention network: Involved in top-down control of sensory processing (endogenous orienting). FEF, IPS, visual and auditory cortices Ventral attention network: Involved in stimulus-driven control (exogenous orienting). VFC, TPJ, visual and auditory cortices Connection between IPS and TPJ All bidirectional
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- How are ERPs modulated by attention? Participants fixate a cross and either focus their attention on the upper left or upper right corner. If the visual stimulus (target) appears within the spatial location of covert attention, the P1 amplitude is larger than when it appears in the unattended location.
- Describe the relationship between atentional Focus and oscillations (alpha and gamma activity). Pps perform a random dot task with different dots on both hemifields. A cue tells them whether they should attend to the left or right random dot circle. Alpha activity decreases and gamma activity increases in the contralateral hemisphere (contralateral to attentional focus).
- Explain the link between attention and awareness with the model of Dehaene et al. (2006). Name all four conditions of the model. There are four conditions in the model: Subliminal unattended: Top-down attention absent + bottom-up stimulus strength weak or interrupted Subliminal attended: top-down attention present + bottom-up stimulus strangth weak or interrupted Preconscious: top-down attention absent + buttom-up stimulus strength sufficiently strong Conscious: top-down attention present + buttom-up stimulus strength sufficiently strong Awareness is linked to top-down attention to a sufficiently strong stimulus (Conscious condition). This is associated with activity spreading to a frontal-parietal network. In contrast, non-aware conditions (e.g. attending to a very weak sensory signal, inattention to a strong sensory signal) are linked to varying levels of activity in sensory cortex alone.