On the organization of Semantic memory in the human brain

Neuroimaging evidence suggests that left hippocampal areas show an increase in activity during semantic memory tasks. Damage to areas involved in semantic memory result in various deficits, depending on the area and type of damage. It has been found that category specific impairments can occur where patients have different knowledge deficits for one semantic category over another, depending on location and type of damage. Category-specific impairments might indicate that knowledge may rely differentially upon sensory and motor properties encoded in separate areas .Category-specific impairments can involve cortical regions where living and nonliving things are represented and where feature and conceptual relationships are represented.
In this paper,
"Functional magnetic resonance imaging (fMRI) was used to examine the pattern of cortical activity during a picture naming task. Subjects (n=12) had to covertly name either animals or furniture items. Functional scanning was performed using a conventional 1.5-Tesla whole-body MRI system. Images obtained during naming the two categories were compared using a non-parametric test. The study revealed evidence for domain-specific lexical regions in left middle, right middle and inferior frontal areas, as well as in superior and middle temporal areas. The results corroborate neuropsychological data and demonstrate directly and non-invasively in human volunteers that semantic representations in frontal and temporal areas are, to some degree, localized and possibly implemented as multiple maps. A completely distributed storage of semantic information is rendered unlikely."
This goes in the favour of the idea that specific regions for episodic memory might just exist in the human brain and may not simply be an emergent property of semantic memory,as such.
I side with the idea that visual knowledge is most probably not a single attribute domain. Under this revised description of visual knowledge, in which visual knowledge itself is a distributed representation, a different set of predictions emerges: objects with multiple sources of knowledge about their appearance (e.g., vision, touch, actions) will be less susceptible to loss of any single source of visual knowledge .
Allport's cloud :
Damage to ventral visual processing regions, which represent only one source of information, will not necessarily cause an impairment to other representations of appearance for these things. This idea was present in Allport's (1985) description of attribute domains (he used the example “cloud”), but it was not included in many sensory-functional theories that, in effect, collapsed across all types of visual knowledge.
What I think:
1.Neuroimaging experiments need to be conducted on infants and lower animals,so as to understand better the organization of semantic memory.
2.Episodic memory,if present separately,alters the organization of semantic memory.Such evolutionarily favourable alterations must be passed on from generation to generation to obtain more advanced forms of semantic memory.
3.We dissect our thought process,when we listen to the word,say,"dog"When i think of a dog I think of a figure with drooping ears ,a set of sharp teeth and a wagging tongue.Also,some may imagine its complete body and think of a four legged entity.It is easy to see that these ideas are composed of semantic chunks:the semantics of "teeth,"tongue","four-legged ness" ,etc.But to a person,who was once badly bitten by a dog,the word "dog" would instill memories of that episode,for many,many years after the incident.In that person's brain the Allport cloud of the word dog,would have a major portion of itself lying in the tactile,than in the visual region.
4.The key to resolving all issues,is to find,how exactly,the notion of time,past and present,is encoded in the brain.
The usual references:
MITECS and wikipedia