By: Brittney Bergeron

The Case of Phineas GageTamping rod entered his left cheekNo perceived damage initially

He could see, hear, smell, and his memory, speech, and comprehension were unaffected

Dr. Harlow realized Phineas was blind in his left eye and his personality had changed drastically

Phineas’ Brain DamageFront part of his left frontal lobe was damaged

Caused dramatic changes to his personalityAlso damage to his right frontal lobe It’s clear from this study that damage to the front part of

the left frontal lobe was accompanied by damage to the right prefrontal cortex

Other Cases Similar to Phineas’A stockbroker had a tumor that pressed down on his frontal

lobes After surgery:

His senses, movements, speech, and memory were unaffected His personality changed drastically

There was damage to his prefrontal cortex on left and right side

The Prefrontal CortexAnterior part of the frontal lobeDamage leads to faults in the formation and execution of

plans and to unsatisfactory social behaviorA correlation exists between the area damaged and the

effect on behaviorThe loss of the ability to make and execute plans is

associated with damage to the prefrontal cortex

Damage to the Prefrontal CortexPatients with damage to the region on the underside of the

brain are: Impulsive, have poor social judgement, easily distracted,

euphoricPatients with damage to the upper and lateral surface of

the cortex are: Apathetic, have difficulty suppressing wrong responses, lack

insight, have difficulty imagining alternative scenarios, have problems recalling the order of recent events

Attention Involves selectionWe pay attention to what’s important for determining our

behaviorThe switching of attention can be:

Stimulus driven Centrally driven

NeglectNeglect is when we ignore useful information involuntarilyOne-sided neglect is when patients with brain damage

particularly in the parietal lobes (usually the right) neglect stimuli on the opposite side of the body

Two types of one-sided neglect: Left-sided neglect Right-sided neglect

Left-Sided NeglectLeft-sided Neglect is when patients are asked to copy

something, they only copy the right-hand half, and if the drawing contains several separate things, they may copy the right-hand half of each thing.

Edoardo Bisiach and Claudio Luzzatti conducted an experiment on two people with left-sided neglect

A patient with Left-Sided Neglect and a right parietal lesion might read the word “train” as “rain” and “willow” as “pillow”.

Left-Sided NeglectAn example of someone with left-sided neglect:

Right-Sided NeglectRight-sided neglect is when patients are asked to copy

something and they only copy the left-hand half.Alfonso Caramazza and Argye Hills described a woman

with a left-sided brain lesion and right-sided neglect: Difficulty with the ends of words When words were in mirror-reversed form, she still had

difficulty with the ends of words Had difficulty with ends of words when letters were arranged

vertically

Is There A Cure for Neglect?There is no cure, but patients with left-sided neglect

improve while either cold water is trickled through the left ear or warm water is trickled through the right ear.

Attention at the Cellular LevelPaying attention to a small part of the visual field is

accompanied by significant changes in the behavior of nerve cells in the parietal lobes and secondary visual areas, and these changes may be useful in noticing things and in localizing them within the visual field. Shows that parietal lobes and secondary visual areas are the

centers for attention in the brain. Damage to these areas would affect attention

The Binding ProblemHow can we tell when several edges, or features of other

kinds (textures, colors, patterns of movement) correspond to the same object or part of the object?

There are two hypotheses concerning the binding problem: Focus attention Synchronized firing

Focused AttentionBinding is achieved by scanning the scene with a spotlight

of attention and features under the spotlight are features of the same object.

Weaknesses: Does not fit well with the impression that we are immediately

aware of the conjunction of features that correspond to an object.

Leaves the mechanism of attention and control of its direction unexplained

Example of the Failure of Binding: Focused Attention

Anne Treisman observed a patient, RM, who had failed in binding different visual features. This shows that an impairment of visual attention can interfere

with spatial localization to prevent binding.

Synchronized FiringNerve cells that respond to different features of the same

object fire synchronously, and that synchrony indicates that the features are those of the same object.

Weakness of synchronized firing: Even if it is true that synchronized firing of cells indicates that

their activity is the result of stimulation by the same object or part of the object, it is not clear how the synchronization is established.

Example of Synchronization that Reflects Binding

Charles Gray recorded from nerve cells in two places in a cat’s primary visual cortex. The images of the bars were aligned in three ways and the

results were: With the two bars moving in opposite directions, there was no

synchronization With the two bars moving in the same direction, there was slight

synchronization With the one long moving bar, there was strong synchronization

This shows that synchronization reflects binding

Binocular RivalryWhen two dissimilar patterns are presented to your eyes,

as if from the same place, and you see alternates between the two patterns which change every few seconds.

Nikos Logothetis and Jeffrey Schall did an experiment with binocular rivalry on monkeys in which they trained the monkeys to report the direction of movement when two gratings drifted in the same direction(no rivalry) and then exposed them to gratings drifting in opposite directions.

Binocular Rivalry (Continued)There are also experiments of binocular rivalry that deal

with stationary patterns.David Leopold and Nikos Logothetis conducted an

experiment similar to this kind on monkeys.