According to Uecker, Mangan, Obrzut, and Nadel (1993), brains of people with DS are different from that of people who grew typically as they have a reduced weight, an abnormal shape, and abnormal convolutions. The authors also note that in a brain of a person with DS, it is hard to distinguish the cerebral cortex and neurons tend to have an immature appearance. In their research, Uecker et al. (1993) hypothesized that hippocampal function (HF) was involved in cognitive deficits in people with DS. The authors note a functional HF should be able to successfully navigate through space with the help of one to two environmental cues.
According to Roizen (as cited in Roberts, Price, and Malkin, 2007), two-thirds of children with DS suffer hearing loss. Children with DS are said to recall less information about a story when there was only audio to present the information (Roberts et al., 2007). In a study done by Laws and Hall (2014), 48 children with down syndrome, between two and four years old, were assessed on how their language and speech were affected with early hearing loss. While there were 48 participants, only 41 (15 boys and 26 girls) were part of the results. The people assessing the children in this study had no knowledge of the children’s hearing history. Of the 41 children that the results of the study was based on, 16 has severe hearing difficulties/deficits. Laws and Hall (2014) found speech accuracy in children with DS was affected by early hearing loss. The authors also found decreased language abilities in children with DS to solely be from language deficits, but also from early hearing loss. The authors also believe that children with DS who have hearing loss as well as speech and language difficulties should take part in therapy. A study done by Zeisel and Roberts (2003) found children with down syndrome experienced more Otitis Media than other children with disabilities. The most notable was in bilateral Otitis Media (Zeisel ; Roberts, 2003). Phelan, Pal, Henderson, Green, and Bruce (2016) looked at different cases of children with down syndrome in regards to hearing loss. In the three cases the authors chose to pay close attention to, only one case was eligible and would gain benefits from receiving a MED-EL Flexsoft cochlear implant. The case involved a female with DS diagnosed after birth who was found to have profound hearing loss with the Auditory Brainstem Response (ABR) scoring system. After the implantation surgery, Phelan et al. (2016) found the patient could recognize auditory/environmental sounds, but still prefered sign language to communicate. Prior to treatment, the patient used sign language as her dominant form of communication.
Language ability is also affected in people with DS. Roberts et al. (2007) reports some people with DS can be in the pre-linguistic phase for their lifetime. Stoel-Gammon (as cited in Roberts et al., 2007) found the babbling stage of a baby’s pre-linguistic ability can last for the first two years, or more, for a person who is born with DS. Roberts et al. (2007) also note there are different part of linguistics that are affected in people with DS. These areas include phonology, pragmatics, semantics, and syntax. Phonology has to do with the sounds of speech (phonemes) and how those sounds are put together to form different words (Roberts et al., 2007). Citing several studies, Roberts et al. (2007) noted that while children with DS have an impacted language ability due to the genetic disorder, they still go through the same process of phonology as non-DS children do, but at a slower rate. Pragmatics is described as how a person uses language in different contexts and forms communication (Roberts et al., 2007). Roberts et al. (2007) reports that in comparison to the other areas of linguistics, pragmatics tends to be a strength for people with DS. However, not all studies on this topic are in agreement about the findings (Roberts et al., 2007). Semantics is the area in linguistics that involves the meaning of words (Roberts et al., 2007). Semantics also includes vocabulary knowledge and knowing concepts in both events and objects (Roberts et al., 2007). Roberts et al. (2007) cites several studies showing that children with DS have a slower rate of gaining vocabulary than that of typically growing children. The author cite the same studies and report children with down syndrome are known to say their first word later in comparison to normally developing children. Syntax is how one puts a phrase and sentences together (Roberts et al., 2007). For children with DS, syntax is a weakness (Roberts et al. 2007). Along with this, Berglund et al. (as cited in Roberts et al., 2007) states children with DS tend to have issues with producing grammatical morphemes as well as producing less verbs than children who do not have DS. While syntax is a weakness of children with DS, several studies cited by Roberts et al. (2007) note that children with DS do tend to grow in syntax continually. As Roberts et al. (2007) and other researchers have shown, children with DS have many difficulties when it comes to linguistics.