Brain occipital lobe

Named for the bones of the cranium under which they lie, the lobes are conspicuously defined by prominent sulci of the cortex, which have a relatively constant position in human brains. Each lobe is specialized for different activities (see Figure 6.3). Located in the anterior portions of the hemispheres, the frontal lobes are responsible for voluntary motor activity, speaking ability, and higher intellectual activities. The parietal lobes, which are posterior to the frontal lobes, process and integrate sensory information. The occipital lobes, located in the posterior-most aspects of the cerebrum, process visual information, and the temporal lobes, located laterally, process auditory information. 

As we move forward, it will prove helpful to get some basic aspects of the human nervous system in place. An enormous amount of work has gone into making associations between brain anatomy and function. Starting with the three main parts of the brain, we know that the cerebrum is the seat of consciousness. It is divided into two hemispheres, which are linked by the corpus callosum. In a very general sense, the left hemisphere is associated with intellectual and the right hemisphere with emotional responses. Within the cerebrum, one can associate a number of brain areas (the prefrontal, frontal, temporal, parietal, and occipital lobes, for example) with functions including vision and hearing. One can make crude maps in which function is mapped onto brain structure. 

Fig. 7. Anatomical organization of dopamine Di mRNA expression in the adult human brain (whole hemisphere horizontal images) at a dorsal (A) and ventral (B) level. Notice strong cortical expression of this dopamine receptor subtype in addition to the intense expression levels in the striatum (CN, Pu and NAc). Adapted from Hurd et al. (2001). aCg, anterior cingulate Amy, amygdala Cb, cerebellum cc, corpus callosum CN, caudate nucleus Cun, cuneus F, frontal lobe Hip, hippocampus hyp, hypothalamus I, insular cortex mPFC, medial prefrontal cortex mm, medial mammillary nucleus NAc, nucleus accumbens O, occipital lobe Phg, parahippocampal gyrus Pu, putamen SN, substantia nigra T, temporal lobe U, uncal gyrus.

The posterior cerebral artery supplies the occipital lobe and portions of the medial and inferior temporal lobe. The arterial supply of the spinal cord is derived from the vertebral arteries and the radicular arteries. The brain is supplied by the internal carotid arteries (the anterior circulation) and the vertebral arteries, which join at the pon tomedullary junction to form the basilar artery (collectively termed the posterior circulation). The brainstem is supplied by the posterior system. The medulla receives blood from branches of the vertebral arteries as well as from the spinal arteries and the posterior inferior cerebellar artery (PICA). The pons is supplied by paramedian and short circumferential branches of the basilar artery. Two major long circumferential branches are the anterior inferior cerebellar artery (AICA) and the superior cerebellar artery. The midbrain receives its arterial supply primarily from the posterior cerebral artery as well as from the basilar artery. The venous drainage of the spinal cord drains directly to the systemic circulation. By contrast, veins draining the cerebral hemispheres and brain stem drain into the dural sinuses. Cerebrospinal fluid also drains into the dural sinuses through unidirectional valves termed arachnoid villi. 

A baby was born missing its right ear and external auditory canal. At 20 months an MRI scan of the brain showed focal atrophy and encephalomalacia of the right parieto-occipital lobe. His mother had used topical tretinoin (Retin A 0.025%) on her face and a large surface of the back before conception and during the first 2-3 months of pregnancy. His father had used oral isotretinoin before conception. 

NMR has been used to measure metabolite levels in the dorsolateral prefrontal area of the brain in patients with bipolar disorder. The ratios of NAc, Cho and ml to tCr were measured in bilateral 8 cm voxels in 20 bipolar patients and 20 age- and gender-matched controls. The ratio of NAc/tCr was found to be lower in both hemispheres of patients compared to control subjects. The levels of NAc in the brains of 21 adult subjects (12 medication-free bipolar affective disorder patients and 9 controls) have been measured with NMR. An increase in NAc content was observed following 4 weeks of Li" treatment. This increase was observed in all regions studied, including the frontal, temporal, parietal and occipital lobes. 

Anterior Cingulate Gyrus. C Frontal Lobe. D Parietal Lobe. E occipital Lobe (primary visual cortex), f Temporal Lobe most of this area of the cortex is on the outside of the far side of the brain, hidden in this view. G Cerebellum. H Thalamus. Encircling the Thalamus are the Hippocampus, the Amygdala, the Basal Ganglia and other parts of the limbic system. l Pons. 3 Midbrain, area in which are found the various brain stem nuclei including the Raphe Nuclei, the Locus Coeruleus, the Substantia Nigra, etc. K Medulla. 

Focal lesions often involve vision. Patients with temporal lobe lesions at times cannot perceive movement, although they can see stationary objects. Photons entering the eye are converted into electrochemical processes that create action potentials that progress to the occipital lobes, where visual information is integrated with information in the temporal and occipital lobes. The electrical and chemical activities in the brain determine one s thoughts, feelings, goals, plans, and actions, which we call consciousness. 

The back portion of the human cerebrum, comprised by the parietal (P), temporal (T), and occipital (O) lobes, is the sensuous portion of our brain. It is devoted to processing all the sights, sounds, smells, tastes, and touch-based sensations that we consciously experience. It connects those experiences to each other and with our memories and emotions. So thank your parietal lobes for being able to feel the hands of your masseur (or masseuse), your occipital lobes for seeing him, and your temporal lobes for hearing his voice. 

The brain is divided into several areas that specialize in different functions. Some of the major sections of the brain are the frontal lobe, the parietal lobe, the temporal lobe, the pons, the medulla oblongata, the occipital lobe, and the cerebellum. The spinal cord connects the brain to the body via millions of nerves that transmit information between the brain and the rest of the body. 

Structural manifestations of phenylalanine neurotoxicity include dysmyelination in the white matter of the brain, revealed with MRl as intense lesions and cortico-subcortical atrophy on T2-weighted images with specifically high-signal intensity in periventricular white matter. White matter abnormaUties may be explained by cytotoxic edema and dysmyelination changes with increase in free water trapped in myeUn sheaths [44]. The size and distribution of WMA vary between patients with locahzation in the white matter of temporal and occipital lobes as the most common areas affected [42] (Figs. 9.5 and 9.6). 

Significant differences of Alpha power were observed at the C3 and Cz channels in the central sulcus, and at the 01 channel in the left of the occipital lobe as shown in Fig. 11.23. In the C3 channel, the mean of the difference is less than zero at 80% confidence level, which indicates that Pattern 2.1 triggered less Alpha power in the left of the central sulcus. However, in the Cz channel, the mean of the difference is over zero at 85% confidence level, which shows that Pattern 2.1 triggered higher Alpha power in the centre of the central sulcus. In the 01 channel, the mean of the difference is less than zero at 90% confidence level, which means that Pattern 2.1 triggered lower Alpha power than Pattern 3.2 in this brain location. 

Significant results of Theta power were also found in most areas of the brain, including the frontal lobe at channels Fz and F4, the Cz and C4 channels in the central sulcus, the P3, Pz and P4 channels over the parietal lobe, and the 01, 02 channels over the occipital lobe, as shown in Fig. 11.28. The mean of the observed differences is over zero at above 85% confidence level, which indicates that Pattern 3.1 evoked significantly higher Theta power than Pattern 3.2 in these areas of the brain. 

Significant differences of Delta wave power were observed in five electrode channels as shown in Fig. 11.33. They are the Fpl and Fp2 channels in the prefirontal lobe, the C4 channel at the right of the central sulcus, and the 01 and 02 channels over the occipital lobe. The mean of the difference in these channels is less than zero at 80% and 85% confidence levels, which shows that Pattern 4.1 evoked less Delta power than Pattern 4.2 in these locations of the brain. 

Significant differences of Beta power were observed over the prefrontal lobe at the Fp 1 and Fp2 channels, on the right of the firontal lobe at the F4 channel, and on the left of the occipital lobe at the 01 channel, as shown in Fig. 11.36. The mean of the difference in the Fpl channel is over zero at 90% confidence level, which shows that Pattern 4.1 triggered significantly higher Beta power on the left of the prefrontal lobe. However, the mean of the difference in the Fp2, F4 and 01 channels is less than zero at 95% confidence level, meaning that Pattern 4.1 evokes lower Beta power on the right of the prefrontal and frontal lobes and in the left of the occipital lobe of the brain. 

---