Occipital Lobe Damage Research Articles

Transsynaptic Ganglion Cell Degeneration in Adult Patients After Occipital Lobe Stroke.

Loss of retinal ganglion cells after occipital lobe damage is known to occur through transsynaptic retrograde degeneration in congenital lesions; however, studies of this phenomenon in acquired pathology, such as strokes affecting postgenicular visual pathway, are scant. We studied a cohort of adult patients with known onset of occipital lobe stroke to look for the presence, rate, and timing of macular ganglion cell loss on optical coherence tomography. Retrospective review of patients seen in tertiary neuro-ophthalmology practice with homonymous hemianopia secondary to occipital lobe stroke of known onset. Optical coherence tomography of the macular ganglion cell complex (GCC) was performed, and hemifields corresponding to the side of the visual field (VF) defect were compared with the control retinal hemifield. Fifteen patients with homonymous VF defects were included in the study, and 8 of these (53.3%) demonstrated GCC hemifield thickness of less than 90% on the side corresponding to VF loss including 2/9 (22%) patients who had a stroke less than 2.5 years ago and 6/6 (100%) patients who had a stroke longer than 2.5 years ago. The amount of hemifield atrophy correlated to the logarithm of time since stroke onset ( P =0.030) but not age ( P = 0.95) or mean deviation on VF ( P = 0.19). Three patients with longitudinal data showed GCC thinning rates of 1.99, 5.13, and 5.68 µm per year. Transsynaptic retrograde degeneration occurs after occipital lobe stroke as early as 5.5 months after injury and was observed in all patients 2.5 years after stroke.

Increased Visual Sensitivity and Occipital Activity in Patients With Hemianopia Following Vision Rehabilitation.

Hemianopia, loss of vision in half of the visual field, results from damage to the visual pathway posterior to the optic chiasm. Despite negative effects on quality of life, few rehabilitation options are currently available. Recently, several long-term training programs have been developed that show visual improvement within the blind field, although little is known of the underlying neural changes. Here, we have investigated functional and structural changes in the brain associated with visual rehabilitation. Seven human participants with occipital lobe damage enrolled in a visual training program to distinguish which of two intervals contained a drifting Gabor patch presented within the blind field. Participants performed ∼25 min of training each day for 3–6 months and undertook psychophysical tests and a magnetic resonance imaging scan before and after training. A control group undertook psychophysical tests before and after an equivalent period without training. Participants who were not at ceiling on baseline tests showed on average 9.6% improvement in Gabor detection, 8.3% in detection of moving dots, and 9.9% improvement in direction discrimination after training. Importantly, psychophysical improvement only correlated with improvement in Humphrey perimetry in the trained region of the visual field. Whole-brain analysis showed an increased neural response to moving stimuli in the blind visual field in motion area V5/hMT. Using a region-of-interest approach, training had a significant effect on the blood oxygenation level-dependent signal compared with baseline. Moreover, baseline V5/hMT activity was correlated to the amount of improvement in visual sensitivity using psychophysical and perimetry tests. This study, identifying a critical role for V5/hMT in boosting visual function, may allow us to determine which patients may benefit most from training and design adjunct interventions to increase training effects.SIGNIFICANCE STATEMENT Homonymous visual field loss is a common consequence of brain injury and is estimated to affect more than 230,000 people in the United Kingdom. Despite its high prevalence and well-described impact on quality of life, treatments to improve visual sensitivity remain experimental, and deficits are considered permanent after 6 months. Our study shows that behavioral changes following vision rehabilitation are associated with enhanced visually-evoked occipital activity to stimuli in the blind visual field. Unlike previous behavioral studies, we observe clinical changes that are specific to the trained region of vision. This lends significant weight to such training paradigms and offers a mechanism by which visual function can be improved despite damage to the primary visual pathway.

Retrograde degeneration of visual pathway

Optical coherence tomography (OCT) gives the opportunity to examine retrograde degeneration of visual pathway damaged at various levels. To estimate OCT data on retrograde degeneration of visual pathway damaged at various levels. Ganglion cell layer (GCL) thickness was measured by OCT in 79 patients with visual pathway damaged at various levels and known duration of visual disturbances. Twenty-One patients were diagnosed with traumatic lesions of the optic nerves and/or chiasma. Fifty-eight patients had retro-genicular visual pathway damage. Thirty-three patients were examined for postoperative homonymous hemianopia after surgery for drug-resistant temporal lobe epilepsy. Twenty-five patients were diagnosed with occipital lobe damage following stroke (12 patients), surgery for arteriovenous malformation (11 patients) and traumatic brain injury (2 patients). All patients underwent assessment of visual acuity, automatic static perimetry, MRI/CT of the brain. Retinal ganglion cell complex was analyzed during OCT. GCL thinning following anterior visual pathway damage was detected in 20 out of 21 patients after ≥22 days. In case of post-genicular visual pathway damage, GCL thinning was found in 25 out of 58 patients (9 out of 33 ones after surgery for temporal lobe epilepsy and 16 out of 25 patients with occipital lobe lesion). After surgery for temporal lobe epilepsy, minimum period until GCL thinning detection after previous visual pathway damage was 3 months, in case of occipital lobe lesion - 5 months. Retrograde visual pathway degeneration is followed by GCL thinning and depends on the level of visual pathway lesion.

Remote spatial and autobiographical memory in cases of episodic amnesia and topographical disorientation

A number of theories have postulated that there is a strong relationship between episodic memory and spatial processes mediated by the hippocampus. Evidence for episodic amnesia following damage to the medial temporal lobes is extensive, but less is known about the types of spatial memory affected by damage to these regions. In this study, we compared episodic memory with detailed scene memory, landmark recognition and schematic (map-based) spatial memory in a group of individuals with amnesia related to damage to the medial temporal lobes (MTL) including the hippocampus. We compared their performance to matched controls, and to an individual with topographical disorientation, a selective spatial memory deficit relating to more posterior temporal and occipital lobe damage. For individuals with MTL lesions, impairments to scene memory were comparable to those in episodic memory. Landmark recognition was impaired only for less familiar landmarks, and schematic spatial memory was not impaired compared to controls. Despite the absence of hippocampal damage, the individual with topographical disorientation, like the MTL amnesic patients, demonstrated impairments to scene memory and recognition of less familiar landmarks, and intact schematic spatial memory, but with less severe episodic memory loss. These results highlight the similarities between detailed scene memory and episodic memory, including their reliance on the medial temporal lobe, and suggest that more schematic forms of spatial memory may be unaffected by medial temporal damage. In addition, the results suggest that damage to more posterior temporal or occipital regions that leads to spatial memory deficits may entail some impairment to episodic memory even if the hippocampus is spared.

“Your body, your choices”: Peer and professional support for breastfeeding

We aimed to identify the factors that can predict the risk of occipital lobe damage preoperatively when resecting tumors located at the tentorial or pineal regions with the occipital-transtentorial approach (Poppen approach).In 27 consecutive patients who underwent tumor resection with the Poppen approach for tentorial or pineal region meningiomas, the following morphologic parameters were assessed on a preoperative magnetic resonance imaging: (1) tentorial angle, (2) tentorial length, and (3) the shortest distance from the confluence of the sinus to the tumor. These parameters, together with tumor size, texture, and resection extent, were correlated with occipital lobe damage by using the one-way analysis of variance, χ2, or Fisher's exact tests.The mean value was 55.3° ± 5.6° (range, 45°–66°) for the tentorial angle, which was significantly associated with the occipital lobe damage grades (P = 0.008), but this was not the case for the tentorial length (P = 0.802) and the shortest distance from the confluence of the sinus to the tumor (P = 0.695). Interestingly, age was also strongly associated with occipital lobe damage risk (P = 0.020). The patients in the subgroup with no occipital damage (grade 4) were the youngest (aged 47.3 years), compared with other grades, with age of 58.0 years for grade 1, 54.3 years for grade 2, and 58.6 years for grade 3. These 2 parameters were also significant after multivariate analysis. No correlation was observed between either tumor nature or the extent of resection and damage grades.The risk of occipital lobe damage increases in the presence of a steep tentorial angle during the Poppen approach for tentorial or pineal area tumors. Awareness of such anatomic features preoperatively is important for minimizing operative complications.

Significance of the Tentorial Alignment in Protecting the Occipital Lobe with the Poppen Approach for Tentorial or Pineal Area Meningiomas.

We aimed to identify the factors that can predict the risk of occipital lobe damage preoperatively when resecting tumors located at the tentorial or pineal regions with the occipital-transtentorial approach (Poppen approach). In 27 consecutive patients who underwent tumor resection with the Poppen approach for tentorial or pineal region meningiomas, the following morphologic parameters were assessed on a preoperative magnetic resonance imaging: (1) tentorial angle, (2) tentorial length, and (3) the shortest distance from the confluence of the sinus to the tumor. These parameters, together with tumor size, texture, and resection extent, were correlated with occipital lobe damage by using the one-way analysis of variance, χ2, or Fisher's exact tests. The mean value was 55.3° ± 5.6° (range, 45°-66°) for the tentorial angle, which was significantly associated with the occipital lobe damage grades (P= 0.008), but this was not the case for the tentorial length (P= 0.802) and the shortest distance from the confluence of the sinus to the tumor (P= 0.695). Interestingly, age was also strongly associated with occipital lobe damage risk (P= 0.020). The patients in the subgroup with no occipital damage (grade 4) were the youngest (aged 47.3 years), compared with other grades, with age of 58.0 years for grade 1, 54.3 years for grade 2, and 58.6 years for grade 3. These 2 parameters were also significant after multivariate analysis. No correlation was observed between either tumor nature or the extent of resection and damage grades. The risk of occipital lobe damage increases in the presence of a steep tentorial angle during the Poppen approach for tentorial or pineal area tumors. Awareness of such anatomic features preoperatively is important for minimizing operative complications.

Sodium pyruvate protect occipital cortex of rats with repetitive and severe neonatal hypoglycemia detected by high resolution 1H nuclear magnetic resonance spectroscopy

Objectives To investigate the occipital cortex metabolite alterations in repetitive and severe neonatal hypoglycemia rats treated with sodium pyruvate and to reveal the protective role of sodium pyruvate using high resolution 1H nuclear magnetic resonance spectroscopy. Methods Thirty-six 2-day-old Sprague-Dawley rats were randomly divided into hypoglycemia group and pyruvate group with 18 rats in each group. Rats in both groups received intraperitoneal injections of insulin (40 U/kg body weight) at 2, 4 and 6 days of age to induce severe hypoglycemia (blood glucose value ≤1.4 mmol/L). In the hypoglycemia group, 2.5 hours after insulin injection, intraperitoneal injection of 50% glucose (2 ml/kg) was administered to terminate hypoglycemia, while in the pyruvate group, 50% glucose (2 ml/kg) and sodium pyruvate solution 2.5 ml/kg (500 mg/kg) were injected. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay was used to observe the status of injured neurons in six neonatal rats, and metabolite changes in occipital cortex of the other 12 rats were detected by 1H nuclear magnetic resonance spectroscopy. The difference between the two groups was compared by independent-samples t test. Results Neonatal rats of both groups reached severe hypoglycemia level 2.5 hours after insulin injection. Compared with hypoglycemia group, pyruvate group had fewer injured neurons (45±5 vs 113±12, t=0.782, P=0.013) and lower injured index in the occipital cortex (0.15±0.03 vs 0.36±0.06, t=1.143, P=0.020). Pyruvate group showed significant decreases in the concentration of taurine [(13.31±2.06) vs (18.44±3.86) mol/kg, t=8.231], glutamine[(1.50±0.24) vs (2.02±0.40) mol/kg, t=3.137], glutamate[(7.04±0.95) vs (9.40±1.73) mol/kg, t=6.449], aspartate[(1.51±0.28) vs (2.15±0.58) mol/kg, t=2.561] and creatine [(6.37±0.99) vs (8.46±1.77) mol/kg, t=4.226] in the occipital cortex (all P'<0.017). Conclusions Simultaneous use of glucose and sodium pyruvate to terminate hypoglycemia in repetitive and severe neonatal hypoglycemia rats can effectively alleviate severe hypoglycemia-induced occipital lobe damage via regulating excitatory amino acid neurotransmitters, energy metabolism and other metabolic pathways. Key words: Hypoglycemia; Pyruvates; Occipital lobe; Magnetic resonance spectroscopy; Animals, newborn

Three Cases with Visual Hallucinations following Combined Ocular and Occipital Damage

Charles Bonnet syndrome is an underrecognized disease that involves visual hallucinations in visually impaired patients. We present the cases of three patients who experienced complex visual hallucinations following various pathomechanisms. In two cases, diagnosis showed coexistence of occipital lobe damage with ocular damage, while in the third case it showed occipital lobe damage with retrobulbar optic neuritis. Theories of pathogenesis and the neuroanatomical basis of complex visual hallucinations are discussed and supported by literature review.

THE PUPIL LIGHT REFEX IN ACQUIRED HOMONYMOUS HEMIANOPIA

AimTo study the characteristics of pupillary responses in patients with homonymous hemianopia following acquired post-geniculate lesion.MethodsEighteen individuals were recruited and were divided into two groups:(1) Eleven patients with acquired homonymous...

The time course of retrograde trans-synaptic degeneration following occipital lobe damage in humans

Following damage to the human post-geniculate visual pathway retrograde trans-synaptic degeneration of the optic nerve fibres occurs. It has been known for some time from investigations carried out in primates that a decline in the number of retinal ganglion cells follows occipital lobectomy. However, this is not detectable in all species studied and whether this occurs in humans was controversial until recent studies that have shown that following lesions of the occipital lobe, the retinal nerve fibre layer thickness measured by optical coherence tomography is reduced and corresponding shrinkage of the optic tract can be demonstrated by magnetic resonance imaging. The time course of the degeneration in humans is, however, unknown. In the present study, we have used optical coherence tomography to demonstrate for the first time progressive thinning of the retinal nerve fibre layer following occipital lobe/optic radiation damage due to stroke. First, in a group of 38 patients the measurement was taken on a single occasion at a known time interval since the stroke, ranging from 6 days to 67 years. Here, a negative straight line relationship (linear regression r = 0.54, P < 0.001) was found between nerve fibre layer thickness and elapsed time since injury in log years, giving a rate of decline of 9.08 µm per log year after adjusting for age. This indicates a decelerating rate of loss that differs from the rate of decline found with chronological age in this same group, which shows a steady rate of thinning by 0.4 µm per year (P = 0.006) after adjusting for duration of the disease. In a second study serial measurements were taken following the acute event in a group of seven patients with homonymous hemianopia; here a negative straight line relationship was found between time and nerve fibre layer thickness in micrometres over a period of data collection beginning at a mean of 36.9 days post-stroke (range 5-112) and ending at a mean of 426.6 days post-stroke (range 170-917). Evidence from clinical observation (funduscopy) suggested that retrograde trans-synaptic degeneration occurred in humans only where the damage to the post-geniculate pathway occurred prenatally. The results reported herein add weight to the previous demonstration that this type of degeneration does indeed occur in the human visual system by showing that it can be monitored over time and hence may provide a model for trans-synaptic degeneration in the human central nervous system.

Perceptual and anatomic patterns of selective deficits in facial identity and expression processing

Whether a single perceptual process or separate and possibly independent processes support facial identity and expression recognition is unclear. We used a morphed-face discrimination test to examine sensitivity to facial expression and identity information in patients with occipital or temporal lobe damage, and structural and functional MRI to correlate behavioral deficits with damage to the core regions of the face-processing network. We found selective impairments of identity perception in two patients with right inferotemporal lesions and two prosopagnosic patients with damage limited to the anterior temporal lobes. Of these four patients one exhibited damage to the right fusiform and occipital face areas, while the remaining three showed sparing of these regions. Thus impaired identity perception can occur with damage not only to the fusiform and occipital face areas, but also to other medial occipitotemporal structures that likely form part of a face recognition network. Impaired expression perception was seen in the fifth patient with damage affecting the face-related portion of the posterior superior temporal sulcus. This subject also had difficulty in discriminating identity when irrelevant variations in expression needed to be discounted. These neuropsychological and neuroimaging data provide evidence to complement models which address the separation of expression and identity perception within the face-processing network.

Ventral extra-striate cortical areas are required for human visual texture segmentation

A patient (HJA) with bilateral occipital lobe damage to ventral cortical areas V2, V3 and V4 was tested on a texture segmentation task involving texture bar detection in an array of oriented lines. Performance detecting a target shape was assessed as the orientations of the background lines had increasing orientation noise. Control participants found the task easier when the background lines had the same orientation or only slightly shifted in orientation. HJA was poor with all backgrounds but particularly so when the background lines had the same or almost the same orientations. The results suggest that V1 alone is not sufficient to perform easy texture segmentation, even when the background of the display is a homogeneous texture. Ventral extra-striate cortical areas are needed in order to detect texture boundaries. We suggest that extra-striate visual areas enhance the borders between the target and background, while also playing a role in reducing the signal from homogeneous texture backgrounds.

Retrograde trans-synaptic retinal ganglion cell loss identified by optical coherence tomography

There is experimental evidence of trans-synaptic retrograde degeneration of retinal ganglion cells following retrogeniculate visual pathway lesions in primate studies. Retinal nerve fibre loss in congenital homonymous hemianopia in humans is well recognized from clinical observation but the findings in acquired lesions have been controversial. Forty-eight persons were recruited and divided into three groups. Two groups were patients with retrogeniculate lesions. In the first group, the occipital damage had occurred during childhood or in adult life whilst the lesions in the second group were congenital. Inclusion criteria for the retrogeniculate lesions included: age >18 years at time of testing; homonymous hemianopia; no other ophthalmic or neurological disorder; and neuroimaging demonstration of occipital lobe damage. The third group had normal visual function. Measurement of the thickness of the peripapillary retinal nerve fibre layer by optical coherence tomography has been carried out in both eyes of each subject. The primary outcome is the peripapillary retinal nerve fibre layer thickness (RNT) in microns. The mean RNT in the eyes with temporal hemianopia (here called the 'crossing-fibre defect' eyes) is 79.8 mu (SD = 35.1 mu) in the acquired and 72.7 mu (SD = 33.2 mu) in the congenital. The mean RNT in eyes with nasal hemianopia (here called the 'non-crossing-fibre defect' eyes) is 83 mu (SD = 29.5 mu) in the acquired and 73.4 mu (SD = 26 mu) in the congenital. In the control group, the RNT measured 101.4 mu (SD = 36.6 mu) for the left eyes and 100.8 mu (SD = 35.4 mu) for the right eyes. In both crossing-fibre defect eyes and non-crossing-fibre defect eyes the mean RNT is significantly greater in the controls than in the hemianopia groups (P < 0.001). These data confirm that there is thinning of the retinal nerve fibre layer following both congenital and acquired lesions of the retrogeniculate visual pathway in humans. This is most likely to represent retinal ganglion cell loss in both congential and acquired groups. Furthermore the magnitude of the thinning is similar in both groups despite the fact that clinical observation has consistently found evidence of RNT thinning in cases of congenital but not in cases of acquired pathology. The data have also been analysed in 12 sectors around the optic disc: it has been shown that the RNT thinning follows the known trajectories of the crossing and non-crossing retinal ganglion cell axons approaching the disc.

Tunnel Vision and Topographic Disorientation after Bilateral Occipital Lobe Damage

Abstract A patient is reported with bilateral visual field loss after infarctions in the territory of both posterior cerebral arteries. Central vision recovered after a period of complete cerebral blindness. The patient then suffered from severe topographic disorientation and impaired colour vision. The similarity of the present case with a famous patient reported by Forster in 1890 was striking and therefore deserved further investigation. Both patients will be described in detail and compared with other selected cases from the literature. The discussion will focus on the problem of macular sparing, impairment in colour perception and topographic disorientation. The dissimilarities between the two patients, which mainly concern simultaneous perception, will also be taken into consideration.

Tunnel vision and topographic disorientation after bilateral occipital lobe damage

Tunnel vision and topographic disorientation after bilateral occipital lobe damage

Tunnel vision and topographic disorientation after bilateral occipital lobe damage

A patient is reported with bilateral visual field loss after infarctions in the territory of both posterior cerebral arteries. Central vision recovered after a period of complete cerebral blindness. The patient then suffered from severe topographic disorientation and impaired colour vision. The similarity of the present case with a famous patient reported by Forster in 1890 was striking and therefore deserved further investigation. Both patients will be described in detail and compared with other selected cases from the literature. The discussion will focus on the problem of macular sparing, impairment in colour perception and topographic disorientation. The dissimilarities between the two patients, which mainly concern simultaneous perception, will also be taken into consideration.

Prepulse effects on the photic eyeblink reflex: evidence for startle-dazzle theory.

Weak visual prestimulation effects on the early (R50, 50-80 ms) and late (R80, 80-200 ms) components of the eyeblink response to bright light flashes were studied in 16 normal individuals. At a lead time of 120 ms, R50 was inhibited relative to no-prepulse control trials, whereas R80 was facilitated. According to the proposed startle-dazzle theory, luminance onset transients trigger an initial response, R50, that is functionally related to startle. Sustained stimulation then activates prolonged eyelid (R80) and pupil responses, which serve to minimize retinal bleaching. Although the sensitivity of the photic blink reflex to attention is controversial, R50 latency showed a pattern suggestive of inhibition of return (Posner & Cohen, 1984, Attention and performance, Vol. X, pp. 531-556, Hillsdale, NJ: Erlbaum). Analyses in a patient with unilateral occipital lobe damage supported previous evidence that inhibition by a visual prepulse requires neocortex, but facilitation does not.

Hallucinations following occipital lobe damage: The pathological activation of visual representations

Neuropsychological investigation of hallucinations may provide insight into the nature of these subjective phenomena, as well as inform theories of perception and recall. We studied a man who described continuous visual hallucinations of object fragments (e.g., lines, corners, patterns) in the left visual field following a stroke in the right occipital cortex. The subject performed normally on standardized measures of visual perception and other cognitive abilities. He had no personality disturbance, and EEG during hallucinations was normal. Review of our records of 211 cases with focal lesions involving visual cortex revealed 5 patients with similar complaints. The hallucinatory experience of such patients probably reflects pathological activation of neural ensembles in the regions bordering an occipital lesion. These regions are presumed to contain records of visual feature fragments which are co-activated by feedback projections in the earliest visual association cortices, where they produce meaningful patterns during normal recall.

Effects of Age and Hemianopic Visual Field Loss on Driving

With the use of an interactive driving simulator, we examined the driving performance of older patients with either homonymous or quadrantic hemianopsia with primarily occipital lobe damage resulting from cerebrovascular accidents (CVA's). We compared the performance of these patients with that of a normally sighted, age-similar control group and that of a normally sighted younger group. The driving performance of the patients was either worse than, or similar to, that of the older control group; all of the older individuals (both patients and normally sighted subjects) had worse performance than the younger group. Age-related effects combined with the effects of visual field losses in older patients with cerebrovascular accidents had a negative impact on driving skills.

Visual Hallucinations in Patients with Macular Degeneration

Objective: This study was undertaken to determine the prevalence of visual hallucinations in patients with macular degeneration, describe such hallucinations phenomenologically, and possibly determine factors predisposing to their development. Method: Using a case-control design, the authors screened 1 00 consecutive patients with age-related macular degeneration f or visual hallucinations. Each patient with visual hallucinations was matched to the next three patients without hallucinations. The patients and comparison subjects were compared in terms of scores on the Beck Depression Inventory, Eysenck Personality Questionnaire, Telephone Interview for Cognitive Status, and a structured questionnaire including demographic characteristics, family history, and medical and psychiatric history. Ophthalmologic data were obtained by chart review. Results: Of the I 00 patients, 1 3 experienced visual hallucinations. Four variables were significantly associated with having hallucinations: living alone, lower cognition score, history ofstroke, and bilaterally worse visual acuity. Hallucinations were not associated with family or personal history of psychiatric disorder or with personality traits. In 1 1 (84.6%) of the 13 patients, the hallucinations had begun in association with an acute change in vision. Conclusion: These results indicate that visual hallucinations are prevalent among patients with macular degeneration. They appear unrelated to primary psychiatric disorder. The predisposing factors of bilaterally worse vision and living alone support an association with sensory deprivation, while history of stroke and worse cognition support a decreased cortical inhibition theory. (Am J Psychiatry 1992; 149:1701-1706) V isual hallucinations are associated with a variety of lesions at all levels of the visual system (1-3). Weinbenger and Grant (2) reported visual hallucinations in patients with pituitary tumors pressing on the optic nerves and chiasm, noting that the hallucinations were not limited to the area of visual field loss. Lance (4) reported visual hallucinations in patients with homonymous field defects and noted that the hallucinations were confined to the area of visual field loss in all but one patient. Because the calcanine area of the occipital lobe was infarcted in many of these patients, he concluded that it was not the origin of the hallucinations and suggested that the surrounding visual association cortex was. Kolmel (5) reported that 13% of 120 patients with homonymous hemianopia and occipital lobe damage experienced complex visual hallucinations in the hemianopic field. The subjects