## 1 Introduction
Although no consensus has been reached as to where V-STM resides in the human brain, there is evidence indicating that the posterior parietal and inferior temporal regions are involved in the retention of visual information (see [14; 15; 16]). In contrast to the wealth of data and theoretical progress relating to verbal STM, there has been comparatively less research exploring the issue of serial order in the visuospatial domain [17]. Moreover, there is now increased interest in visual STM for serial order for various kinds of nonverbal stimuli. Several experiments investigated the involvement of STM in its variants depending on (i) different sensory input and output modalities (e.g., auditory-verbal, visual-verbal), (ii) the presence/absence of either articulatory suppression or distractors, (iii) the request to remember not only the items shown (STM for item, henceforth, MI) but also the order in which they were presented (STM for order, henceforth, MO) [18; 19; 20; 21]. Item and order are two critical dimensions of STM. MI usually consists of the units that define the information to be retained. On the other hand, serial order information (MO) concerns information about the temporal sequence of units within a list of stimuli. Forward serial order seems to be the preferred mechanism of memory to recall information, even when the tasks do not require it [22; 23]. Neuroimaging studies also reveal the involvement of distinct neural substrates for the retention of item and serial order information and possibly shared neural substrates for the retention of serial order information in verbal and visual-spatial modalities [20]. There is evidence supporting the existence of an STM network in retaining an abstract representation of serial order information, independently of content information, namely, the nature of the item to be remembered, which is stored separately [24]. Serial order hasbeen specifically studied to explain how verbal items are encoded in the phonological loop system. These verbal codes, being sound-based and inherently sequential, represent information about individual phonemes as well as about their serial order by keeping track of the associations among temporally adjacent items. Behavioural, neuropsychological, and neuroimaging evidence was discussed by [PERSON] [25]. The aforementioned evidence points to (i) two separate buffers of verbal and visual-spatial short-term memory subsystems [5; 26], (ii) distinct neural substrates for the retention of item and serial order information, and (iii) shared neural substrates for the retention of serial order information in verbal and visual-spatial modalities [20]. This provides new interpretation keys to better understand the processes involved in learning and, more importantly, in specific learning disorders. Memory and working memory are involved in fluid reasoning [18; 27; 28] and in a variety of academic problems and clinical conditions that affect children and adolescents (e.g., [29; 30; 31]). Indeed, there is substantial evidence that WM and STM impairments play a critical role in mediating some of the academic problems in children with Reading Disabilities (RDs) and Math Disabilities (MDs) (for a review, see [32; 33; 34]). More specifically, serial order STM is responsible for the storage and retrieval of the phonemes constituting a new word in the correct order and thus contributes to the development of long-term phonological representations [35; 36; 37]. Moreover, sequential processing abilities recruited in serial order STM tasks play a critical role in language development and vocabulary learning (see [35; 36]). Other studies have shown a correlational relationship between measures of phonological loop function and both first and second language acquisition [37; 38; 39]. Crucially, STM in its various expressions is a factor that may increase or decrease the likelihood of co-occurring reading, spelling, and calculation difficulties in children with specific learning disorders [40].