Attention

Contents

  1. Definition and Core Concepts
  2. Types of Attention
  3. Neuroanatomical Substrates
  4. Clinical Evaluation and Testing
  5. Pathophysiology and Clinical Syndromes
  6. References

Definition and Core Concepts

Attention is a highly distributed, foundational cognitive function that is essential for the effective operation of almost all other cognitive domains, including memory, language, and executive function. In clinical practice, the terms concentration, vigilance, and persistence are frequently used synonymously with attention.

It is generally accepted that attention is an active, effortful, and selective process that is closely linked to a patient's intention and state of arousal. Without adequate attention, sensory inputs cannot be properly encoded into memory, leading to secondary cognitive failures.

Brain map illustrating the fronto-parietal attention networks

Attention relies on a distributed neural network, heavily involving the right prefrontal cortex, the thalamus, and the ascending reticular activating system (ARAS).

Types of Attention

Clinically and neuropsychologically, a distinction is made between different types of attention, which rely on overlapping but distinct neural networks:

  • Sustained Attention (Vigilance): The ability to maintain a consistent behavioral response during continuous and repetitive activity over an extended period.
  • Selective Attention: The ability to maintain a cognitive or behavioral set in the face of competing, distracting stimuli (focusing on one conversation in a noisy room). This is closely tied to working memory.
  • Divided Attention / Executive Function: The ability to respond simultaneously to multiple tasks or multiple task demands (multitasking), requiring rapid shifting of attentional resources.

Neuroanatomical Substrates

The neuroanatomical substrates of attention are widely distributed rather than localized to a single brain region. The core components of the attentional network encompass:

  • The Ascending Reticular Activating System (ARAS): Located in the brainstem, this system is responsible for maintaining basic wakefulness and arousal.
  • The Thalamus: Acts as a sensory relay and gating station, filtering which sensory inputs reach the cortex.
  • The Prefrontal and Parietal Cortex: The multimodal association cortices, particularly in the right hemisphere, are critical for directing, sustaining, and dividing attention.

Damage to any of these interconnected areas—whether from stroke, trauma, or metabolic derangement—may cause significant attentional impairment.

Clinical Evaluation and Testing

In the presence of severe attentional disorder, it is extremely difficult, if not impossible, to make any meaningful assessment of other cognitive domains (e.g., memory or language), as the patient cannot engage with the testing process. Therefore, attention is usually tested first.

Attentional mechanisms may be tested in a variety of ways. Standard "bedside" tests primarily look for defects in selective attention and working memory. Common assessments include:

  • Orientation in time and place.
  • Digit span testing (repeating strings of numbers forwards and backward).
  • Reciting the months of the year backward.
  • Counting backward from 30 to 1.
  • Serial sevens (serial subtraction of 7 from 100, e.g., 100, 93, 86, 79, 72, 65).

Pathophysiology and Clinical Syndromes

Impairment of attentional mechanisms leads to distractibility. This often results in a patient complaining of a "poor memory" because information was never attended to or encoded in the first place—a state better termed aprosexia.

Severe attentional deficits can also lead to disorientation, perceptual problems, and behavioral issues such as disinhibition. The cardinal neurological disorder of attention is delirium (acute confusional state), which is characterized by a fluctuating level of arousal and profound inattention.

Besides delirium, attentional impairments are frequently seen following traumatic head injury, metabolic encephalopathies, and in ostensibly "alert" patients with neurodegenerative diseases like Alzheimer’s disease. In the latter, the deficit often presents as an impaired ability to divide attention, a core feature of the dysexecutive syndrome.

 

References

Parasuraman R. Attentional functioning in Alzheimer’s disease. In: Morris RG, Becker JT (eds.). Cognitive neuropsychology of Alzheimer’s disease (2nd edition). Oxford: OUP, 2004: 81-102

Perry RJ, Hodges JR. Attention and executive deficits in Alzheimer’s disease: a critical review. Brain 1999; 122: 383-404

Scholey A. Attention. In: Perry E, Ashton H, Young A (eds.). Neurochemistry of consciousness: neurotransmitters in mind. Amsterdam: John Benjamins, 2002: 43-63

 

Cross References

Aprosexia; Delirium; Dementia; Disinhibition; Dysexecutive syndrome; Frontal lobe syndromes; Pseudodementia