The occipital The occipital lobes Occipital lobe - Mahidol University

23/06/542. Tests for dysfunction (cont)-Macular sparing indicates that the lesioninvolves the occipital cortex, rather than theoptic radiations. Occlusion of the posteriorcerebral artery should be suspected.-"Filling in" of a scotoma may be tested bypresentation of a horizontal line crossing thevisual field with a gap in the scotomatousarea. Patients report seeing a completed lineif filling in occurs.NEUROPSYCHIATRY 1272. Tests for dysfunction (cont)- Eye movement can be tested by having thepatient follow a moving target.- Occipital lobe and posterior occulomotorlesion patients can do this; frontal lobe oranterior ocularmotor lesion patients cannotfollow the verbal command with voluntaryfollowing.- Right occipital lesions will not follow intothe left half field.NEUROPSYCHIATRY 1282. Tests for dysfunction (cont)Forced choice (guessing) discriminationof a stimulus may result in identificationof objects within a scotoma, although ifasked to identify a stimulus the patientreports he does not see it.B. Areas 18 and 19NEUROPSYCHIATRY 129NEUROPSYCHIATRY 130Tests for dysfunction-Sensory deficits such as rapid visual fatigue,impaired visual adaptation, and raised visualthresholds indicate involvement of 18 or 19.-Visual l following is tested by looking foropticokinetic nystagmus generated byfollowing moving vertical black lines on awhite background.Tests for dysfunction (cont)Unilateral spatial agnosia is tested bypicture copying (details on the left may beomitted) or card sorting (cards on the left areignored).NEUROPSYCHIATRY 131NEUROPSYCHIATRY 13222