Spatial Neglect: Fellini Case Study

• The presentation focuses on attention in an over-stimulating and noisy world.

Federico Fellini as a Case Study

• Federico Fellini was a well-known Italian director, born 1920 and died in 1993.
• A CT scan of Fellini's brain at the age of 73, one week after his right-hemisphere stroke, showed right temporo-parietal damage.
• Fellini's stroke resulted in neglect of one side of space, including a severe motor deficit (paralyzed left arm), sensory deficit in the left part of his body, and a left visual field defect.
• The Rey-Osterrieth complex figure test showed Fellini's unilateral neglect.
• Fellini was able to detect a wiggling fingertip in the far left or far right visual field.
• When both fingertips were wiggling in the far left or far right visual field, Fellini could only detect the movement on his right side.
• Simultaneous stimulation of both the left and right visual fields caused extinction of the sensory information in the left visual field.
• Spatial neglect involves the inability to process and perceive stimuli towards the contralesional side of the body or environment when competing stimuli are on the ipsilesional side.

What is Attention?

• William James (1890) stated: "Everyone knows what attention is..."
• Munsell (1873) stated: "On attention discourse at length; it's na familiar to every thoughtful"
• Pashler (1998) stated: "No one knows what attention is, and there may not be an it there to be known about (although of course there might be)."
• Instead of attempting to define attention, its effects on cognitive functions are studied.

Filter Metaphor: Cocktail Party Phenomenon

• The ability to focus on one stimulus while filtering out others has been called the cocktail party effect.
• At noisy parties, people can focus on one person's conversation despite many conversations happening simultaneously.
• In a Dichotic Listening Task or shadowing task, different messages are presented to different ears, and the listener is instructed to repeat or shadow one of the two messages.

Broadbent's Filter Model of Selective Attention

• Sensory memory holds all incoming information for a fraction of a second and then transfers it to the filter.
• The filter (bottleneck) identifies the attended message based on physical characteristics such as the speaker's tone of voice, pitch, speed of talking, and accent.
• Only the attended message passes through to the detector.
• The detector processes the information from the attended message to determine higher-level characteristics, such as its meaning.
• Neisser's work on selective attention in vision showed that when participants are presented with two sequences of films simultaneously as transparent layers, they can follow one while ignoring the other.
• The Dear Aunt Jane experiment challenged Broadbent's filter model
• Instead of reporting "Dear 7 Jane" presented to the attended ear, participants reported hearing "Dear Aunt Jane," showing the importance of top-down processes.

Binocular Rivalry

• In a typical binocular rivalry paradigm, an observer views two different static images in the two eyes
• Under ordinary viewing conditions, a subjective visual experience will stochastically switch between the two images, with full dominance of one image followed by full dominance of the other.

Treisman's Attention Model

• Treisman's model is a modification to Broadbent's model.
• Physical characteristics of sounds (e.g. pitch, speed) and language and meaning can be used to separate attended and unattended messages.
• In the dictionary unit, words have a threshold for being activated.
• Names have a lower threshold to get activated.

Late Selection Models

• MacKay 1973 provided evidence for a late-selection model, in which the filter of attention is after the meaning is processed.

A Shift of Perspective in Attention Studies by Lavie

• The ability to selectively attend to a task can depend on both the distracting stimulus and on the nature of the task (Lavie, 2010).
• Processing capacity refers to the amount of information people can handle, which limits their ability to process incoming information.
• Perceptual load relates to the difficulty of a task (low-load versus high-load tasks), depending on factors like practice and difficulty.

Perceptual Load Theory of Attention

• In a high-load task, no resources remain to process other stimuli so irrelevant stimuli can't be processed/have little effect.
• Thus, high-load tasks result in less distraction.
• With an easy, low-load task, the remaining processing capacity can process task-irrelevant stimuli, which leads to distraction.