Selective attention IIIII

What core features of psychopathology affect selective attention

• Lesions

• ADHD

• Schizophrenia

What is hemispatial neglect

• Neurological syndrome associated with unilateral cortical lesions, (lesions on one side)

• Affects 2/3 acute right hemisphere stroke patients

• Presents as a lack of awareness of objects and events contralateral (opposite) the causal lesion

• Eg a right lesion would make an individual unaware of their left side

• Deficits in neglect provide a window on attention and spatial representation

How can spatial coordinates be coded in relation to hemispatial neglect

• Spatial coordinates is the position

• Can be coded relative to:

• The individuals centre of gaze (retinotopic)

• An objects central axis (midline)

• Other objects in the scene (alocentric)

• Deficits in neglect provide a window on attention and spatial representation

Hemispatial neglect (Driver and Halligan, 1991)

• When showed visual images patients failed to detect differences on left side of image that fell on the right side of visual midline

• Spatial deficits in hemispatial neglect appear to operate in multiple and dissociable coordinate systems

• Magnitude of neglect is also effected by non spatial stimulus attributes

How does hemi spatial neglect affect neural circuits

• Deficits associated with extinction and neglect reflect physical damage to neural circuits

• Extinction reflects relative activation rather than absence of response to visual stimulus

• Attentional not perceptual deficit

Attention and psychopathology

• Deficits in attention also characterize many psychiatric syndromes

• Inhibitory deficit of irrelevant stimuli is a core feature of schizophrenia and ADHD

Selective attention and ADHD

• As ADHD is associated with impulsivity and impaired attention control, central deficits are associated with sustained attention and response inhibition

• These have been attributed to disrupted fronto striatal circuits

Features of ADHD regarding selective attention

• Individuals with ADHD have reduced prefrontal volumes compared to controls

• Shows reduced activation in frontal and cingulate regions

• Inhibition of irrelevant information and pre potent responses are crucial for goal directed behavior

(Rubia et al, 2005) selective attention and ADHD

• Used fMRI to contrast neural activation during response inhibiton and error detection in ADHD

• Sampled 16 medication naive adolescents with ADHD and age matched healthy controls

• The ADHD group were slower to respond on go trials and faster to respond on stop trials

• They also made more errors of omission and had more variable RT’S

(Rubia et al, 2005) selective attention and ADHD brain region reults

• Data revealed differential activation of neural circuits associated with attentional control in ADHD

• Reduced activation of prefrontal cortex and anterior cingulate during successful inhibition

• Reduced activation of cingulate cortex when inhibition fails

• Cingulate cortex is associated with dynamic allocation of attention (flexibility)

(Rubia et al, 2005) selective attention and ADHD neurophysiological reults

• Evidence of altered neurophysiological function despite task difficulty being equated and lack of medication in ADHD group

• Changes in neural activation correlated with parental ratings of children on the strengths and difficulties questionnaire

• ADHD is characterized by a distinct pattern of activity across networks of cortical areas associated with attention and control