What does research on sensory deprivation and restored vision reveal about the effects of experience on perception?

Sensory deprivationleads to changes in the organization of the brain and the deafferented cortices occupied with other remaining sensory inputs and the subsequent processing related to them (de Heering et al., 2016; Litovsky & Gordon, 2016; Stronks, Nau, Ibbotson, & Barnes, 2015). Cortical areas that are related to the deprived sensory modality, as usual, are involved with other remaining sensory afferent pathways and this reorganization has been defined as “cross- modal plasticity”. The cross- modal plasticity may not necessarily be associated with the improvement of the remained sensory functions (Lee et al., 2014).

The problem of a sensory deprived individual is not limited to the sensation. The sensory information is used for subsequent perceptual and cognitive functions and the paucity of these sensory inputs may affect the subsequent cognitive functioning. There are two approaches to explain the interaction between sensory information and cognitive functioning. In a bottom-up approach, cognitive functions are rooted in the sensory information and the lack of sensory experience may leads to an impairment in subsequent cognitive functioning (Valentijn et al., 2005). In a top- down approach, cognitive functioning modulates the sensory processing (Kamiyama, Fujita, & Kashimori − Biosystems, 2016; Näätänen, Tervaniemi, Sussman, Paavilainen, & Winkler, 2001) and the brain can compensate the lack of sensory information and interpolate the information loss based on the remained parts (Baltes & Lindenberger, 1997). Furthermore, there are two variations for the interaction between these approaches that may be considered as two alternative perspectives. The former considers a horizontal relationship between the bottom- up and the top- down systems and states that both of them may be related to the same source (Christensen et al., 2001). The latter considers a parallel relationship between these two systems in a way that both of them work along as “perceptual reversals”. For example, in the matter of visual perception, the bottom-up visual process scans the visual field on the basis of saliency and similarity, and the top-down process tries to achieve the goal (Kornmeier, Maira Hein, & Bach, 2009).

The visual information engages more than 35 centers and 50 percent of the brain for processing (Kandel & Showartz, 2002). The loss of this information in blindness provides an opportunity for the evaluation of the effects of visual deprivation on cognitive performance. Both perceptual and cognitive abilities of individuals with blindness could be explained by two controversial mechanisms including the compensation and the general loss. In the compensation approach, individuals with blindness show a preference to the remaining healthy tactile (Goldreich & Kanics, 2003), auditory (Vercillo, Milne, Gori, & Goodale, 2015), and olfactory systems (Zhou, Fang, Pan, Liu, & Ji, 2017), as well as the subsequent cognitive functioning such as auditory skill (Fieger, Röder, Teder-Sälejärvi, Hillyard, & Neville, 2006), arithmetic and working memory (Dormal, Crollen, Baumans, Lepore, & Collignon, 2016), and semantic and episodic memory (Pasqualotto, Lam, & Proulx, 2013). This compensatory phenomenon is apparent in the cortical level as the occipital lobe is activated by auditory and tactile stimuli (Reich, Maidenbaum, & Amedi, 2012; Stronks et al., 2015).

On the other hand, the general loss approach states that individuals with complete blindness show significant impairment in different cognitive tasks such as tactile spatial memory (Vecchi & Girelli, 1998), tactile spatial attention (Forster, Eardley, & Eimer, 2007), selective and divided spatial attention (Collignon, Renier, Bruyer, Tranduy, & Veraart, 2006), semantic and phonemic verbal fluency (Nejati & Asadi, 2010), and general cognitive skills (Nejati, 2008).

Aging is another life experience that influences sensory and cognitive functioning. The process of ageing has a degenerative effect on sensory impairment such as age-related hearing loss (Roth, Hanebuth, & Probst, 2011) and visual impairment (Sachdev et al., 2013) as well as the cognitive degeneration including focused and divided attention (Getzmann, Golob, & Wascher, 2016), learning (Nejati, Garusi Farshi, Ashayeri, Aghdasi et al., 2008a, Nejati, Garusi Farshi, Ashayeri, Aghdasi et al., 2008b), working memory (Carryl & Ivan, 2011), and inhibitory control (Kleerekooper et al., 2016). Some studies found the dependence of cognitive performance on the sensory inputs increases with age (Ghisletta & Lindenberger, 2003; Li & Lindenberger, 2002). Indeed, some studies have shown that sensory impairment, especially visual information, causes deficit in a number of cognitive functions. For example, Anstey, Luszcz, Giles et al., 2001 showed that diminished visual acuity, but not auditory acuity, is associated with a decline in memory functioning. The more dependency on visual versus auditory information older adults have, the more general functioning and well- being were observed (Liu et al., 2016).

Age related cognitive and perceptual decline can be investigated through three theories. The first one, the common-cause hypothesis, postulates that ageing as an underlying phenomenon deteriorates both cognitive and perceptual functioning (Baltes & Lindenberger, 1997); the second one, the sensory deprivation hypothesis, considers sensory decline as the origin of cognitive degeneration (Salthouse, 2000), and the third theory is the cognitive degeneration hypothesis which postulates that cognitive decline decreases the capacity for the sensory acuity and the perceptual processing (Raz et al., 2005).

The reorganized brain after sensory deprivation is more dependent on the remaining senses and should perform the cognitive functioning in the absence of the deprived sense. This may empower them more or make them more sensitive to normal life-related threat situation such as ageing. To date, interaction between ageing and blindness as an example of sensory deprivation has not been clearly understood. The present study aims to evaluate the interaction between the ageing process in the individuals suffering from complete acquired blindness. The evaluation of the main effect of age and sensory deprivation in this population, will reveal the most significant factor in cognitive degeneration, that it to say ageing or visual deprivation.

In the present study, some of these hypotheses are tested by comparing the performance of blind and normal vision participants of different age groups in certain cognitive tasks. If blind individuals have higher rates of cognitive decline, the first hypothesis is confirmed that sensory deprivation causes neural and cognitive degeneration. If blind and normal vision participants have similar rates of cognitive decline, the evidence confirms the “common cause hypothesis” and it can be concluded that ageing plays a significantly more important role in cognitive decline than sensory deprivation (blindness). Finally, if blind individuals have lower rates of cognitive decline, resource allocation hypothesis is confirmed which entails that higher engagement of cognitive functions to remediate impaired sensory input is considered to be the main factor responsible for cognitive performance.

In sum, we hypothesized that the different hypotheses of age and deprivation related cognitive degeneration could be studied in the study of ageing in individuals with blindness.

• Stimuli characteristics have a decisive role in our perception and cognition. In the present study, we aimed to evaluate the effects of dimension of stimuli, two-dimensional (2D) versus three-dimensional (3D), on perception and working memory. In the first experiment, using the method of eye tracking, a higher blink rate, pupil size, and the number of saccade for three compared to 2D stimuli revealed a higher perceptual demand of 3D stimuli. In the second experiment, visual search task shows a higher response time for 3D stimuli and an equal performance with 2- and 3D stimuli in spatial working memory task. In the third experiment, four working memory tasks with high and low cognitive and perceptual load revealed 3D stimuli are memorized better in the both low and high load of working memory. We can conclude that 3D stimulus, compared 2D, imposes a higher load on perceptual system, but it is memorized better. It could be concluded that the phenomenon of filtering should occur in the early perceptual system for preventing overload.

• A growing number of studies suggest that patients with depression exhibit tendency to interpret ambiguous stimuli in a relatively negative manner. The purpose of the present study is to develop a practical interpretation bias measure relevant to depression using the mental states behind the facial expressions.

  In the present cross-sectional study, 45 patients with major depression were compared with 50 healthy subjects. A modified version of reading the mind in the eyes test (RMET) with a new scoring system was used for evaluation. Independent t-test and Multi-Factor ANOVA were used for analysis

  Findings showed that individuals with major depressive disorder have generally lower performance in the mind reading (p < 0.001). Furthermore, they scored lower in reading the positive mind (p < 0.001) and the neutral mind (p < 0.001), while obtained higher scores in reading the negative mind (p < 0.05). Interpretation scores revealed that individuals with depression interpreted minds more negatively than it seems (p < 0.001).

  As individuals with depression tend to interpret mental states of others worse than they really are, reading the mind in the eyes test is potentially useful to assess the interpretation bias associated with depression.

• Increasing evidence point to the usefulness of transcranial direct current stimulation (tDCS) in modulating and possibly delaying deterioration in Multiple Sclerosis (MS). Multiple symptoms have been shown to be ameliorated and hold promise for future therapeutic uses of tDCS in MS patients.

  (1) To evaluate in the published literature, the role of transcranial direct current stimulation (tDCS) in the rehabilitation of MS patients, (2) To discuss its possible future position in the enhancement of cognition and working memory in these patients.

  Literature review was done on PubMed from 1990 to March 2018 on the role of neuromodulation of MS by tDCs, using the keywords: “Multiple sclerosis” OR “MS,” AND “tDCS.”

  We first identified 112 articles and their related websites, of which 36 articles were further selected for extensive analysis mainly based on clinical relevance, study quality and reliability, and date of publication.

  Clinical application of tDCS in MS has suggested that it could be potentially useful in relieving much psychological and cognitive impairment to a reasonable extent. Future research and applications of tDCS in this area have to overcome the challenge of what should be the best possible therapeutic tDCS protocol for managing cognitive impairment in MS.

• Placebo response is common in patients with major depressive disorder (MDD) and decreases the likelihood of demonstrating drug superiority over placebo in a randomized, controlled trial (RCT). This paper aims to review the collective evidence for particular patient characteristics and trial features being associated with placebo response in MDD.

  MEDLINE/PubMed publication database and Cochrane Library were searched for meta-analyses of placebo response in MDD, published in English from January 1990 to December 2017. The evidence for factors predicting a low or high placebo response was tabulated and weighted on the basis of methods, results, and quality of supporting studies.

  We identified 58 papers, examining the possible association of 40 different factors with placebo response in MDD. Research methods varied considerably across articles so that our reporting remained descriptive. The evidence for any factor being associated with placebo response in MDD appeared very weak to weak.

  Since none of the pooled analyses that we included could be regarded as a meta-analysis in its strict sense, and analytical approaches varied considerably, the current work is descriptive only, and without formal statistical analysis.

  Despite 25 years of pooling data from RCTs in MDD, there is no single factor for which strong evidence exists that it influences placebo response.

• Lumbosacral plexus tumors (LSPT) are rare lesions whose clinical presentation can be very nonspeci/fic, and which are usually identifiable through imaging exams. In order to facilitate complete tumor resection without loss of neurological function multimodal intraoperative neurophysiological monitoring (MINM) has been employed, although the literature is still scarce and non-systematic. In this paper we aim to briefly review the lumbosacral plexus’ anatomy and describe the strategy adopted for intraoperative monitoring in the treatment of six patients with benign LSPT operated in the last 6 years. In our sudy, all patients improved pain, and none developed motor or sensitive deficit on postoperative period. We consider intraoperative monitoring critical during surgical resection, as a tool for preventing neurological deficit, and improving outcomes, that are particularly important given anatomical and functional significance of lumbosacral plexus tumors.

• Patients with Young onset Parkinson disease patients (YODP) are individuals with motor complications identical to late onset Parkinson’s disease (PD) but onset in early age. YOPD is a specific subgroup of PD and their performance on saccadic eye movements is not well established. This study evaluated saccadic eye movements in patients with YOPD (< 40 years at onset of illness).

  Eye movements were recorded during saccadic eye movement tasks, induced by presentation of a visual target and reflexive saccadic task was administered.

  YOPD patients showed reduced saccadic velocity on reflexive saccadic task (Gap task) as compared to their age matched healthy controls. Additionally, pupil width in gap period and at saccade onset was measured. Pupil width was significantly smaller in patients with YOPD as compared to control subjects.

  Reduced saccadic velocity implies that Parkinson’s disease affects saccadic circuitry in patients with YOPD reflecting impaired circuitry at the brainstem level. The reduced pupillary response in gap condition is attributed to deficits in motor preparedness in patients compared to controls.