Attention

• Hemineglect (hemi-attention): a spatial phenomenon where lesion to one part of the brain results in ALL INFORMATION on the opposite side (contralateral) to the lesioned are ignored.

  ·       Individual could have intact sensory and motor functioning

  ·       The neglect of info occurs with reference to spatial frame.

  ·       This condition often involves damage to the right parietal lobe because the parietal lobe plays in spatial processes.
• Arousal: As in alertness and arousal, one aspect of attention as a concept.

  ·       Involves the ability to extract information from environment or to select a particular response among other possible alternatives

  ·       Alertness and arousal are particularly low when tired or sleepy

  ->  Extreme cases include a coma.
• Selective attention: A category of attention that involves the selection of information essential to a task.

  ·       Often conceptualized as a filtering process that allows us to hone in on critical information from the vast am

  ·       count of information available.

  ·       Includes information we are keeping “in mind” or set of possible responses.

  ·       Cognitive mechanism that allows one to select—from all the possibilities present to one--- the task of comprehension as the most salient aspects of processing that must be accomplished at this time.
• Attention

  ·       A multifaceted process conceptualized in many ways.

  ·       A selective process of information to be further processed.

  ·       Serves to modulate or modify ongoing processing across all domains of function.

  ·       Attentional controls occurs via brain circuits that span many brain regions.
• divided attention: kind of attention that we use when we have to split our attention across tasks. Also known as “multitasking”

  ·       The resource, or effort, that is required to process information is central to this concept.

  ·       Multiple-resource theory: suggest that a limited set of distinct resource pools may exist, each of which can be applied only to certain types of processes meaning that the processing capacity of the brain is larger when tasks DRAW FROM DIFFERENT RESOURCE pools than from the same one (e.g. performing an auditory and visual task simultaneously.
• Reticular activating system (RAS)

  The brain system responsible for overall arousal which is the basic level of attention which requires the nervous system to be RECEPTIVE to stimulation
• Reticular activating system (RAS)


  • Also responsible for sleep-wake cycles
  • Also critical for alertness
• Cells in the ascending RAS connect to the cortex

  1. Dorsal system: travels to the cortex via the thalamus. Relies on the neurotransmitter, acetylcholine, and stimulation of these neurons leads to cortical activation

  2. Ventral route: travels to the basal forebrain and subsequently onto the cortex. Relies on two major neurotransmitter systems= noradrenergic system and the serotonergic system
• Thalamus


  Helps to keep us alert and awake by modulating the level of arousal of the cortex via glutamate (main excitatory NT)
• Parts of the thalamus

  • Medial dorsal, intralaminar, and reticular nuclei. Damage here could be enough to result in coma
• Noradrenergic system


  Brain cells within this system are located within the locus coeruleus of the brainstem. They usually fire at a regular slow rate but firing is increased in response to arousing stimuli and decrease their firing during periods of drowsinesss and sleep. Activity in the locus coeruleus appears to prevent sleep. Lesions here could lead to deficits in cognitive tasks in rats and monkeys. Noradrenergic system has been found to be involved in stress-related aspects of arousal and been implicated in psychiatric disorders like PTSD
• Serotonin (5-HT)


  Another neurotransmitter involved in arousal. Cell bodies located in the raphne nucleus. Subsystem is involved in arousal by aiding in wakefulness and suppressing REM sleep. Cell activity increases during wakefulness and decreases substantially during REM sleep
• Neurons rely on neurotransmitters to relay messages
• Early selection viewpoint


  Attentional selection occurs at an early stage of processing before items are identified
• Late-selection viewpoint


  Selection occurs only later sensory processing is complete and items have been identified and categorized
• Event-related potential (ERP) studies

  • Provide information on when processes occur
  • State that attention selection can occur BOTH earlier and later in processing (not an either-or proposition)
• The neural bases of divided attention, which is the ability to split one's attention between different sources of information or different tasks, remains controversial. Some research suggests that the ability to divide attention is increased when tasks rely on distinct or separate neural processors (e.g., auditory cortex, visual cortex), whereas other research suggests the existence of a central bottleneck, likely associated with operations performed by prefrontal cortex.
• Conceptually, attention is thought to be supported by a network of brain structures. One theoretical model proposes that the reticular activating system maintains vigilance and arousal, the cingulate imparts motivational significance to information (particularly when a task is difficult), the posterior parietal region provides a sensory map of the world, and frontal regions provide motor programs for moving the focus of attention.
• Another model argues for three subsystems. The first involving the locus coeruleus, parietal cortex, and right frontal regions, supports alertness. The second, involving the superior colliculus, superior parietal region, temporoparietal junction, and frontal eye fields, allows attention to be oriented to sensory signals so as to select among them. The third subsystem, involving the basal ganglia, lateral ventral prefrontal region, and the anterior cingulate cortex, supports executive aspects of attention.
• Still other models divide regions between a dorsal attentional subsystem, involved in top-down control of attention; and a ventral subsystem, consisting of temporoparietal cortex and inferior frontal cortex of the right hemisphere, that allows attention to be directed to salient stimuli in the environment.
• The default network, consisting mainly of ventromedial prefrontal cortex, posterior cingulate and the temporal lobe, appears to be especially important when attention is directed inward to thoughts, ideas, and processes related to the self.
• In the hemineglect syndrome an individual ignores information on the side of space contralateral to a brain lesion, It is associated with damage to the ventral attentional network A and connectivity between regions that form part of this network.
• The neglect is not due to sensory deficits, as the severity of neglect for the contralateral side of space does not vary with sensory modality, and individuals with a severe sensory deficit for the contralateral side of space do not exhibit neglect for that side of space
• Neglect can be modulated by factors that draw attention to information on the neglected side of space, such as high emotional saliency, motivational factors, and a need to process such information to gain understanding or comprehension of material.
• Theories regarding the main underlying deficit in neglect include one suggesting that patients lose the mental conception of the negleeted side of space, and another suggesting competition between the attentional biases of each hemisphere to the opposite side of space.
• Treatments for neglect include guided therapy, such as visual scanning therapy to change the individual's allocation of attention; sensory stimulation of the body parts located on the negleeted side of space, to make that side of space more salient; and alterations of brain activity by methods such as transcranial magnetic stimulation. In general, these therapies are aimed at altering the imbalance of activity between the hemispheres.
• Neglect illustrates that attention can be either space-based or object-based. 
• The fact that neglect is more common and more severe after right-hemisphere damage suggests that the right hemisphere is more important for overall arousal and attention, and/or that the attentional gradient for the contralateral versus the ipsilateral side of space is steeper for the left hemisphere than the right.
• Material in the neglected field that cannot be identified by patients with hemineglect can nonetheless influence performance by priming certain responses, and appears to undergo early stages of processing that allow unconscious but not conscious access.
• Our sense of consciousness appears to derive from the integrated and potentially synchronized activity across a wide variety of brain regions