Brain damages demonstrate clearly the existence of independent systems exploring distinct portions of space (Guariglia and Antonucci, 1992)..

Zihl et.al. (1983) have described a patient with a loss of movement vision in all three dimensions. The patient was unable to see moving objects, but could see the objects when they were stationary. It implies that there is a special brain area that is processing the movement of an object in space. The visual area V5 was damaged where the integration of the moving object takes place. The patient had no difficulty to see colors, forms or depth. Even the perception of slow moving objects was impaired. Movement vision for targets travelling along the horizontal plane was somewhat better than for targets moving along the vertical plane. This is in agreement with normal persons indicating that movement sensitivity (at least for low movement speed) in the human field of vision differs for the main axes. The patient never experiences any movement in the periphery. In the V1 there are cells mediating direction-plus orientation selective cells that were intact. Apparently the integration of the movement is occurring in a later stage of visual processing where more global analyses take place. The backward propagation of V5 to V1 must also be damaged. The patient had bilateral cerebral lesions affecting the lateral temporo-occipetal cortex and the underlying white matter. Lesion was more extensive on left. The complaints were difficulty in pouring tea or coffee into a cup, because the fluid appeared to be frozen, like a glacier. Not only the patient could not stop pouring at the right time but also she was unable to perceive the movement (or a pot) when the fluid rose. Furthermore the patient complained of difficulties in following a dialogue because she could not see the movements of the face, and especially the mouth of the speaker. In a room where more than two other people were walking she felt unsecured and unwell, and usually left the room immediately because people were suddenly here or there but she had not seen them moving. The patient experienced the same problem but to an even more marked extent in crowded streets or places, which she therefore avoided as much as possible. She could not cross the street, because of her inability to judge the speed of a car, but she could identify the car itself without difficulty. 'When I'm looking at the car first, it seems far away. But then, when I want to cross the road suddenly the car is very near'. She gradually learned to estimate the distance and moving objects of moving vehicles by means of the sound becoming louder.

A patient with a left side lesion with a right personal neglect had no signs of extrapersonal neglect. She had a lesion in the left temporo-insular region. Her personal neglect was limited to upper limb, the shoulder and the lower limb being totally spared.

This neglect is more close to body and corresponds with other data (Heilman et.al., 1995) that the area close to the body is processed in the left hemisphere and especially in the dorsal part (lower right visual hemifield).

Deficit of seeing things smaller than they are.

A 84-year old lady who, after a right temporo-parietal infarction, complains of seeing things smaller than she expected. (Lilliput sight). This may be a breakdown of size constancy. The ability to adjust the object size to the viewing distance. She had the sensation that object contours were twisted. She systematically underestimates the length of the left segment of horizontally presented pairs and the lower segment of vertically presented pairs. She could image objects with the correct size, when asked to indicate the dimensions of various things she indicated the correct sizes with her hand. She had also no difficulty in estimating the distance between two objects or between the objects and her self. Beside micropsia the patient reported an altered perception of color as if the color were the result of a badly mixed assemblage of different shades.(Ceriani et.al.,1998)

Hemimicropsia is a rare disorder of visual perception characterized by an apparent reduction of the size of objects when presented in one hemifield. Cohen et.al. (1994) reported two cases of hemimicropsia resulting from focal brain lesions. The first patient was an art teacher and could accurately depict his abnormal visual perception. He subsequently died and his brain was examined post mortem. In the second patient, micropsia was assessed by a quantified size comparison task. The size of a given object is normally perceived as constant across any spatial position. Hemimicropsia may thus be considered a limited violation of the size constancy principle.

It refers to the illusion of objects and persons as being farther away than they actually are. (Teleopsis). Its is a consequence of a loss of near vision attentional system. Teleopsis associated to occipito-parietal damage

Palinopsis is the perservance of visual images. A deficit as result of occipito-parietal damage. In normal persons the transient (magno) system is believed to reduce visual persistence by inhibiting the sustained parvo system.

A 66- year-old patient with bilateral inferior temporal lobe lesions has no deficit in the lower visual fields but in the upper visual fields. He had a right hemispatial neglect. When stimuli viewed the superior visual field were brought near, the patient they were not longer extinguished when presented simultaneously with distant lower visual stimuli. This suggests that the patient have neglect for the upper part of the visual field and for the far extrapersonal space. The patient also misreached consistently in the lower right away from the upper and left spatial fields where he manifested spatial neglect. The visual mislocalization was especially in the central field. Normal attention is preferentially distributed away from the body during visual exploration, but distributed towards the body during tactile exploration. (Shelton et.al., 1990)

41 year -old left-handed women complained occasionally to see the lower halves of images she was fixating, i.e. when looking at people she would only see them from the waist. Cows in the field appeared floating in the air without legs. She was unable to perceive more than a single object at the time and could not recognize visual patterns made up of independent elements. She was unable to describe from memory a familiar route to the grocery store. She misreached for targets presented in the visual periphery. However when targets were presented in the foveal region of her eye the deficit was minimal. She had a bilateral parieto-occipital infarction. Her abnormalities suggest that the parietal regions control attention and intention in the lower parts of extrapersonal space. This shows a functional superiority of the upper hemiretinal system that subserves visual function below the horizontal meridian. (Mennemeier et.al., 1992; Rapcsak et.al., 1990)

A 67-year-old women major complaint was that her environment was fragmented. She had an infarct in the left temporo-occipital lobe. She could find her way in her home but only with eyes closed, but she became confused with her eyes open. On one occasion, she attempted to find her bedroom by using a large lamp as a landmark while walking towards the lamp she fell over the dining room table. She was unable to write. She sees only a single letter thus when creating a letter she saw only the tip of the pencil and the letter under construction and lost the previous constructed letter. Television programs bewildered her because she could see only one person or object at the time and therefore could not determine who was speaking or being spoken.

She had a disorder named simultanagnosia, it is characterized by the inability to interpret complex visual arrays despite preserved recognition of single objects. The patient deficit is attributable to limitation in the attention requiring process by which sites marked in a buffer zone (short-term memory) are linked to structural description or word form information. Seeing involves the articulation of stored information with information linked to specific site in the visual short term memory (Coslett and Saffran, 1991).

A women could only perceive one of two objects, but could integrate two related objects into a coordinated action. A pen and its cap presented in the central view of the patient could either see the pen or the cap, but she had no difficulty to pick them up and join them together. The patient has a dysfunction of the central vision. No difficulty is bringing together even unrelated objects in the peripheral presented objects. (Castiello et.al.,1995)

A 52-year-old women patient with a lesion of the right parietal lobe and right thalamus could transpose the number of the clock to the right side design a clock with eyes open. But when asked to perform the same task with eyes close, her clock face was drawn normally. These two examples indicate that visuospatial and visuospatial imagery does not draw upon identical neuronal substrates. The attentional system for extrapersonal space may not be identical to the attentional system for intrapersonal space. This deficit is the opposite to the deficit of the patient described here before (Anderson,1993) .

Angelelli et.al. 1998 reported basic visual impairment in patients with neglect. The sensitivity loss may result from changes in the top-down attentional modulation of lessened higher areas in visual cortices. The primary visual cortex was spared in these patients.

A women with a severe neglect who denied any difference between the drawing of an intact house and that of a burning house when the features relevant for the discrimination on the neglected side. Nevertheless when forced to choose the house in which she would prefer to live she constantly preferred the intact house showing an implicit knowledge for the information she was unable to report (Marshall and Halligan, 1988).

A strange case was reported from a 37-year-old female whose bodily awareness was fragmented. When reading a newspaper and turning the page with the right hand, the left-hand turned back the same page. While eating with the left hand she tried to put more food into the mouth than what she was able to swallow. During swimming she as afraid that the left hand wanted to drown. She also developed disturbances of the body image. Several times a day she sensed a third arm and sometime a third leg. There was also a time delay between the new position of a limb and the appearance of the ghost limb. She also experienced a splitting of her body. When she was rising from a bench she felt that only the right half started walking whereas the left side remained on the bench. Her conscious body image was based on competing activity of more than one brain region. Normally all these brain acting simultaneously but with this patient they had become independent and result in fragmentation of bodily awareness after distorted updating of cerebral representations (Hari et.al, 1998).

There is a difference in processing of visual exploration and mental imagery. By the maintenance of visual mental images there was mental exploration there is a specific participation of the superior occipital cortex, interestingly no activation of the primary cortex. (Mellet et.al..1995)

Two patients were asked to describe from their remembrance the piazza of the Domo in Milan. They were only able to visualize the right part of the piazza even if point of view changed 180 degrees. They could remember the second time what you could not do at the first time. They see the left side but cannot interpret it or describe it. Bisiach and Luzatti (1978)

Figure 1. Deficit in imagery. Looking in the direction from the Domo of Milan is remembering the right side of the piazza (open circles). Looking towards the Domo he is remembering only the other side of the Piazza (dots) (After Bisach et al.1978)

Another example of deficit in imagery is a patient, but strangely not any neglect for stimuli located in a far and near space or on his own body. Contrary with other cases involving imagery disorders the patient showed a lesion confined to the right frontal lobe suggesting that the frontal lobe had to describe mentally a familiar piazza in Rome from a given vantage point. He had also lesions on the anterior temporal lobe and the head of the caudate and lenticular nuclei (basal ganglia). He gave a good account of the right side of the piazza none or a very few of the left side. When asked to do the same from an opposite vantagepoint he reported more elements on the right side. He also misplaced some semantically relevant details from the left to the right side off one of the piazza; that is the ticket office where he had taken a bus to work for 20 years was described as being on the non-neglected side. Strangely enough the patient had no neglect of perceptual or motor neglect or asymmetry in perceiving targets in a far or near space. Also suggesting a role of the frontal lobe in some specific types of mental imagery. (Guariglia and Antonucci, 1992)

A 67-year-old man with a right parietal lobe, showed a deficit in visual imagery, but showed no perceptual or personal neglect (Beschin, 1997).

A 72-year-old woman with a right hemisphere infarction, who could copy a word, but was not capable of reading it aloud. The right hemisphere is specialized for processing of whole or configurations while the left hemisphere is specialized for processing parts of or details. In reading the letter string is treated as a whole while in copying it is processed element by element. (Cubelli and Simoncini 1997).

A 51 year old women, with lesion of the bilateral posterior parietal cortex, having difficulties in cutting nails, brushing her teeth, locking the door, cutting meat wit fork and a knife. Strangely she had no neglect for personal and extrapersonal space or misreaching object in the central and peripheral visual field with either hand. Her deficit contrasted wit normal movement trajectories of the arm during execution of such gestures and with accurate manual prehension in the context of simple reaching movements. She could correctly reach for an object with instructions to only grasp and not use it. However during utilization gestures motor systems must retrieve data from the memory regarding the functional properties of the object. Although the patient recognized objects and their functional properties yet this knowledge cannot trigger the appropriate selection and shaping of fingers. (Sirigu et.al., 1995)

Prosopagnosia is a deficit to recognize familiar faces. The name was give by Bodamer in 1947. Patients could not recognize familiar faces but is not impaired to recognize his personal belonging such as their wallet or comb from similar items owned by others. One prosopagnosic farmer could recognize his friends after recovery but remained unable to recognize his cows. Another farmer could recognize his cows but not his friends (Perrett, 1987).

There are even cells selective for faces, profiles and rotation of the head.

Patients could recognize the voice but not the face of a familiar person. The strange thing is that patients can also defect for other stimuli. They can not recognize their own car and do not recognize different discriminate unfamiliar faces well. Prosopagnosia never occurs with deficit in recognizing faces but make of cars but are able to recognize different types of cars passenger car fore engine an ambulance or a funeral car. They can recognize an automobile as an automobile a cow as a cow or a dress as a dress also the sub component eyes, noses windshields, and wheels. But in the case of human face when they are asked the specific possessor of the visual appearance the process breaks down.

Proposopagnosic patients generated frequent and large electrodermal skin conductance response to faces of persons they previously known but were now unable to recognize them. Their responses were larger than to unfamiliar faces. There are also patients reacting just the opposite. They were able to recognize the identity of the familiar faces but failed to generate electrodermal responses (SCR) to those faces. The first patients had a bilateral occipito-temporal damage whereas the other patients had a ventromedial frontal damage. Two separate neural systems, one for somatic and the other for non somatic information associated with the same stimuli (Tranel et.al., 1995)

In an article of Wurtz et. al. (1982)show four self-portraits of a man with lesions on his parietal (right) side. He ignores objects in the left half of his visual field. He can see the objects but he does not attend to them. The first portrait does not show his left side. The second painting is made three and a half-month later, it shows some part of the left side. The third is painted after six months and the last nine months after the attack.

Figure 2. Self-portraits of a painter with lesion on the right side of the parietal cortex. Half of the face was neglect but gradually the patient improved from the damage. Last portrait (right under is made six months after the stroke.

Two patients were accurate in describing the face and indicating sex and facial expression, but were unable to recognize the familiar faces. They both had bilateral symmetrical lesions in the posterior-inferior part of the hemispheres (Clarke et.al, 1997)

There is dissociation between the identity and the expression of perceiving a face. One patient was impaired at perceiving facial identity, but could not discriminate facial expression and gender from static photos of faces. In contrast performed well when seeing facial expression and gender of moving photos A second patient was good in perceiving the identify of a face but poor in judgment emotional expression from both static and moving faces. Apparently there are separate processes for encoding face identity and facial expression and furthermore there is also a separate encoding for facial expression from moving and static images (Humphreys et.al., 1993).

There is dissociation between the identity and the expression of perceiving a face. One patient H.J.A. was impaired at perceiving facial identity, but was poor at discriminating facial expression and gender from static photos of faces. In contrast performed well when seeing facial expression and gender of moving photos A second patient G.K was good in perceiving the identify of a face but poor in judgment emotional expression from both static and moving faces. Apparently there are separate processes for encoding face identity and facial expression and furthermore there is also a separate encoding for facial expression from moving and static images (Humphreys et.al., 1993).

A patient with a impairments mirrored those of the patient just described. The patient was able to demonstrate how the hand was to be positioned on an object but not for what purpose. (Sirigu et.al., 1991)

A 35 year-old women with a bilateral parieto-occipetal infarct had a deficit in grasping simple objects with a gasping without deficit in reaching toward the location of these objects reaching deficit. The grasp in usual objects was better than for neutral objects. With usual objects the patient could use cognitive cues, based on prior knowledge of the objects. This suggests that semantic cues can be transferred to the pragmatic system. This transfer is possible because numerous anatomical connections exist between these two pathways. The patient could was able to indicate with the fingers the size of objects presented as virtual images through a mirror or te size of imagines usual objects. Apparently two pathways for processing the size of an object: one for perceptual analyses (ventral system) and one for guiding a motor action toward an object (dorsal system) (Jeannerod,1994).

Lesions affecting one of the hemispheres can tell us more of the division of labor between the two hemispheres

Very strange things are happening when the right hemisphere is damaged:

• eating the half their plate
• wash their right side or brush their hair only at the right side
• dressing right part of the body
• reading right part of the paper
• typing only right part of the keyboard
• designing a clock with all the digits in the right part and sometime only the half of the digits
• bumping against furniture in their left visual field. The stimulus appears to come from the opposite non neglected side

Unilateral neglect is more frequent to right hemispheric lesions. The main reason for this asymmetry is that the right hemisphere has attention for both visual hemifields whereas the left hemisphere is more confined to the right side of the world. It has so many tasks for the execution of the spoken word. When the right is damaged the global vision is gone and the left side cannot cope for this loss. Neglect is not blindness to the left side but indifference. A moving finger in the neglected side sometimes can be seeing whereas a static finger is neglected. Ramachadran (1998) describes a very interesting case of mirror agnosia. He holds a mirror is such a way that the neglected side of the world is reflected in the mirror. Seeing a pen in the mirror the she was asked to grab the pen, although she was well aware there was a mirror reflecting the neglected side

She wanted to grab it and by repeating the experiment she said ït was behind the mirror. Later she even tried peeking over the edge of the mirror to look for the pen.

I want to cite again Ramachandran, because he is so fascinated by this disorder.

Mostly strangely is the unawareness of a disease (anosognosia), or a deficit of concern about deficits (anosodiaphoria). Von Monakow first described it in 1885. This deficit can be in different forms: a denial of cortical blindness (Anton syndrome), deafness, hemiplegia (one side of the body paralyzed), word deafness, dyslexia (word blindness) or dysphasia (inability to create word and sentences without losing the capacity to think).

Bisach et.al. (1986) has demonstrated that different forms in anosognosia are dissociated from each other. It shows that anosognosia for left hemiplegia is not simply a manifestation of inattention to the left side of egocentric space and that even patients who are utterly inattentive to this side may fully appreciate their motor impairment (hemianopia). Conversely persisting denial of hemiplegia is compatible with the ability to attend to the left side and to watch the examiner demonstrating the inert drop after release of the passively raise paralyzed limb.

Anosognosia is a disorder that can have some relationships with the unilateral neglect. The patient is not in a state of neglect but denial. In the most extreme cases a patient is not only deny that the limb is paralyzed but says that it belongs to someone other. There area great number of theories of to explain this disorder but nobody really understands it. It is like unilateral neglect almost always associated with the damage of the right hemisphere. Strange enough unilateral neglect and denial can occur independently some patients with neglect do not experience denial and vice versa. As we have seen sometime neglect can be overcome by showing a moving finger. In denial there is no way to change the mind of the patient. They persist in their denials "It is this vehemence of denial that cries for an explanation". To listen to a patient deny ownership of her arm and yet in the same breath admit that it is attached to her shoulder is one of the most perplexing phenomenon that one can encounter as a neurologist. He asks himself why we always betray us constantly. Patients with anosognosia it is extreme but how often we are denying the truth in normal people. The role of the left hemisphere is handling the comprehension of meaning. New information it must be categorized in the preexisting worldview. The left hemisphere mainly does this. It can ignore a conflicting data and the left hemisphere can ignore the threatening information and just deny it. It is always a struggle between stability and instability. The left hemisphere is to create a belief system a modal to fit in the new information or to deny it repress it or confabulate it. The role of the right hemisphere however is more revolutionary in their approach when she feels it does not fit into the old model she wants to revise it. What happens when the right hemisphere is damaged? The left hemisphere can go on their own, without a more or less punishing and correcting honest right hemisphere. Left hemisphere conformist largely indifferent for discrepancies and the right hemisphere highly sensitive to perturbation

During dreams the right hemisphere can bring back memories that are repressed by the left hemisphere.

Bisiach et.al.. (1986) reported two type of unilateral neglect one for extrapersonal and the other to personal space.

Mattingly (1999). Neglect does not show deficit of an isolated visual even on the affected side only when stimuli are presented at both side follows extinction.

Milner and Goodale (1999) are thinking that extinction, neglect and optic ataxia are dissociable disorder of different areas of parietal cortex. Extinction not only SPL but all other areas imbalance between neural circuit in the two hemisphere competition between concurrent stimuli. Activation of circuits in one hemisphere tend to increase in all related circuits

Ogden 1985. Hemineglect right hemisphere more lesions in posterior region whereas left hemisphere neglect in anterior regions. Left more language in posterior areas. Right hemisphere more pronounced for manipulospatial skills and depending on the region of the parietotemporal junction. The region is homologue in he left with the Wernicke's. Right hemineglect is more severe than left hemineglect

Chedru (1973) demonstrated that normal individuals scan a visual array by starting in the upper left quadrant and proceeding systematically in a clockwise circular direction. Left side lesions proceed left to right horizontal or vertical sweeps of the page whereas the right lesion proceed in erratic fashion more this component more disturbed right lesion

This is accordance with other studies where patients with neglect in the left part van the visual field had the most difficulty to attend to the lower left quadrant.

Ladavas et.al.. (1993) convincingly showed that motor neglect and perceptual neglect are lesions in different parts of the brain. For motor neglect more frontal parts, whereas the perceptual neglect in posterior parts of the brain. They also proposed a hyperattentional hypothesis for perceptual neglect. The attention is more attracted to the right side by a right hemisphere lesion. According Kinsbourne (1987) this is due to the fact that the left cerebral hemisphere's bias toward the right hemispace is released from inhibition following right hemisphere damage. They observed that performance of neglect patients on the left side improved when the stimuli on the right were rendered less salient either by removing them from the display or by excluding vision (blindfolded). Patients with motor neglect did not show these effects.

The doctor asks the patient what the color was of the tie. The patient answered blue with red spots. The doctor had no tie. The excuse of the patient was that the light in the chamber was not good to see it properly. A man who throws his leg out of the bed not realizing that it was his leg and was stupefied that he fell out of bed. Normally these patients lack emotional feelings. This concerns patients with right hemisphere lesions. Left hemisphere is reacting normally.