A number of studies investigated the positive effects of cognitive training in healthy older individuals [34,44,45,46,47]. For example, in the ACTIVE study (advanced cognitive training for independent and vital elderly) the main objective was to examine the effects of memory, reasoning, and speed-of-processing training. The participants were randomly assigned to groups and were compared to no-training controls. RCTs were conducted to compare training among different cognitive domains [44]. It was found that each targeted cognitive ability showed a significant improvement as compared to the baseline assessment, and this improvement lasted up to 2 years, as indicated by a post-intervention follow-up [44]. Sustained improvements in specific cognitive domains (memory and reasoning) that lasted up to 5 years after training were further highlighted [48]. Following this line of research additional evidence was provided for the benefits of cognitive training [45]. It was noted that cognitive training can improve cognitive functions of healthy older adults. The observed improvement lasted up to five years after the intervention had begun. The implications of these outcomes were that an improvement in cognitive functions has a positive impact on daily living skills and it can also alleviate depressive symptoms.

An overall improvement of global cognitive function has also been reported, especially after the application of CCT programs in healthy adults, targeting specific cognitive domains such as verbal memory, working memory, attention, etc. [36,49,50,51]. Recently in a pilot study [36] a computerized cognitive stimulation website named VIRTRAEL (“Virtual Training for the Elderly people”, n.d.) was developed. This is a free access platform that includes tests and exercises for the assessment of cognitive skills in older people, such as attention, learning, memory, and executive functions. It was noted that there was an overall improvement of these targeted cognitive functions and it was proposed that CCT is in effect a useful tool that can be used in ‘the fight against cognitive symptomatology associated with aging and neurodegenerative diseases’.

Despite these promising outcomes and the ongoing research carried out in this area, the positive role of CCT’s approaches warrants further consideration. The benefits of computerized cognitive training in healthy older adults are being addressed, but at the same time, the problem concerning the efficacy of this method needs to be further examined, since this issue ‘remains controversial in the scientific community, and both sides of the debate encourage further research’ [52]. 

So far, most studies using technological means to enhance cognitive function in patients with dementia have mainly focused on AD while other types of dementia have been considered to a lesser extent.

In earlier studies [53,54,55,56], the efficacy of computer-based technology in patients with dementia was investigated and the common assumption drawn from these studies was that there was an overall improvement in patients’ cognitive performance. In particular, an overall improvement in patients’ training performance was noted [53], along with an improvement regarding the immediate and delayed recall of objects and routes [54]. In addition, a significant improvement in patients’ cognitive functions such as verbal fluency and executive functions was observed [55]. Improvement in specific cognitive areas has similarly been reported [57] where there was a good performance in the speed of data processing in patients with dementia and an almost normal performance in the comprehension of verbal, short memory, and perception tasks compared to normal subjects’ performance. A study of 20 Korean-speaking patients found that the application of a systematic computer-based cognitive training program may have beneficial effects in various cognitive areas such as language, attention, calculation, verbal memory, and frontal function at least for a short period of time [58]. However, in a systematic review of 31 studies that applied cognitive training in patients with mild or moderate AD, it was suggested that despite the heterogeneity and the variability of the interventions used, the outcome of those studies is that cognitive training may lead to an improvement of global cognition of the patients, particularly when these training programs are longer in duration and more intensive in nature [59]. At the same time, it is suggested that shorter interventions that aim at specific cognitive areas may also lead to an improvement of those particular areas. Other studies further support that computer-based cognitive interventions have a positive effect in the cognitive function of dementia patients and may also target and improve specific cognitive areas [60,61,62].

In relation to the easiness that patients with dementia can use and employ computer-based technology in their daily routine, it was found that the application of a cognitive training protocol is superior to other therapies for the cognitive improvement of patients with dementia [56]. These intervention programs offer patients independence [63] and account for the involvement of patients in leisure activities that promote healthier behaviors [64]. Moreover, it has also been pointed out that it is important to tailor computer activities to each patient’s needs [65]. Similarly, the importance of the development of person-centered tablet programs was noted as an implementation of a new service in dementia care [66].

The utilization of information and communication technologies (ICTs) as tools to enhance the quality of life for both individuals without dementia and those affected by dementia has been investigated [67]. Furthermore, it has been emphasized that the use of technological devices plays a crucial role in promoting a more active lifestyle for people with dementia, benefiting both their physical and mental well-being. In the same vein, [68] concluded that since patients with dementia find their interaction with technology enjoyable, then only interesting and enjoyable activities should be employed along with innovative ways to deliver them to patients with dementia, ways that can mimic real-time communication.

Even though there are a significant number of studies highlighting the positive effects of technological interventions, there are still certain studies that seem to be quite skeptical about the overall benefits that these non-pharmacological methods may in effect have.

The efficacy of computer cognitive rehabilitation in patients with mild cognitive decline was tested and the results indicated that the overall computer-based cognitive training in patients with AD and mild cognitive decline is effective at least in delaying the continuous progression of cognitive impairment in AD [69].

With respect to Greek language and Greek-speaking subjects with dementia, a relevant study presents the results of a computer-based intervention program for people with AD for a period of one year [35]. These patients have been tested before and after each intervention program (pre-test and post-test). The authors compared these data in an effort to examine the way the program performs and at the same time to assess the cognitive skills that may be improved. It was suggested that the patients’ overall scores were preserved for this period of time and they also showed a slight improvement. The authors concluded that the application of the specific intervention program had positive effects on patients’ overall performance.

Overall, the outcomes of the preceding studies indicate that the application of technology is necessary for the development of programs that can improve not only the cognitive impairments of patients with dementia and slow down the progression of the disease, but also provide a better quality of life since it reinforces a level of autonomy that is really important for the patients both emotionally and interpersonally.

Further evidence for the validity of the intervention with cognitive training programs derives from a great body of neuroimaging studies that underlie the importance of the application of these programs in relation to the beneficial effects on the physiology of the brain which are beyond the scope of this work (see for example a review paper of task related fMRI studies [70]; also studies reviewing the importance of specific brain networks and the impact that computer-based training has on them [71,72,73,74]).

One of the most promising rehabilitation strategies that has gained much interest over the last two decades and that is often adopted within the field of dementia care is that of errorless learning. Errorless learning (EL) is an approach used in memory rehabilitation and has its roots in behaviorism and, specifically, in the principles of implicit learning and memory. This approach was initially used in the research of amnestic patients who suffered from impaired explicit memory but had an intact implicit memory [75]. EL relies on implicit memory in the sense that there is no need for a conscious retrieval of information as in explicit memory and the information to be acquired is obtained in a more passive way. Thus, EL minimizes the chance of error production during learning and maximizes the chance of encoding only correct information through modeling, immediate provision of the correct answer, etc. In the literature of EL, the bulk of studies support the effectiveness of this method as it is applied to a variety of clinical populations.

Positive effects of errorless learning have been widely reported, mainly in the clinical population of amnesic patients. However, only two studies [75,76] have examined this technique in relation to cognitive decline in normal ageing. A comparison of the efficacy of errorless and errorful learning on memory performance in older people and young adults showed that there was an overall lower memory performance and flatter learning curves for older adults as compared to young adults, regardless of the task conditions [76]. However, the researchers found a superiority effect of errorless learning as compared to errorful learning, a finding that was equally evident in both groups. They suggested that the prevention of errors during learning results is essentially an effective strategy and may lead to better memory performance.

In a study involving participants with severe memory impairment [75], it was observed that they exhibited a higher capacity to learn items from word lists through errorless learning compared to an errorful control group. This advantage of EL was consistently observed in various case studies, encompassing learning object names, novel face-to-name associations, new facts, names of rehabilitation ward staff, orientation information items, and methods for programming memory aids [77]. These findings were further substantiated by subsequent research conducted with populations of individuals with dementia and those in the early stages of AD, yielding similar outcomes [41,78,79].

Although there may not always be unanimous agreement among researchers regarding the benefits of EL, it is noteworthy that a majority of studies emphasize the efficacy of EL procedures in ameliorating memory difficulties in individuals with dementia. For instance, a review encompassing 26 studies involving individuals with dementia, all employing EL rehabilitation strategies, revealed that even individuals with minimal to moderate dementia can successfully relearn daily life skills and sustain these abilities over an extended period [80]. Additionally, earlier investigations explored the ability of dementia patients to recall familiar faces [81], name objects, and describe their uses [82]. One study, which also aimed to enhance memory for familiar faces, suggested that EL is an efficient method yielding substantial improvements in memory [41,42]. These findings align with the existing literature, demonstrating the effectiveness of errorless learning when compared to other approaches, such as error-prone learning, within patient populations [83,84,85]. Moreover, it is worth noting that the aforementioned studies did not employ technology-based intervention programs. Instead, they established a strong foundation for the development of more efficient tools for the cognitive treatment of dementia. Later studies emphasized the need for the use of computer-based technology in cognitive intervention along with the application of EL method and provided positive results from the combined application of both, suggesting that the EL approach is highly effective for enhancing and promoting memory abilities [43,86]. A study of Chinese-speaking dementia patients found that early AD subjects had an improvement in their overall cognitive function after attending the EL memory program, although the positive treatment effect had a limited duration [87]. It was further supported that older normal adults can benefit from an EL program, as part of a preventive strategy in order to minimize the risk of developing dementia.

Finally, the results of various studies comparing the effectiveness of errorless and trial-and-error methods in acquiring knowledge, ranging from very general to very specific, were presented for both individuals with dementia and healthy participants [88]. It was concluded that the errorless learning (EL) approach appeared to be advantageous for retrieving specific knowledge, but less so for acquiring general knowledge. Furthermore, they noted that not all patients exhibited a consistent response to the learning conditions, suggesting limited applicability of this approach for patients with dementia and restricted efficiency for rehabilitating a broad spectrum of knowledge. These findings warrant further research.

Prospective memory is the ability to remember to perform previously planned actions or certain tasks in the future [89]: for example, to remember and go to an already scheduled appointment, or to remember to call someone and wish for his/her birthday, or to remember to take their medication and so on—the so-called instrumental activities of daily living that ensure independent living. Prospective memory, in effect, comprises two components: the prospective component and the retrospective component. The first one has to do with remembering an action that must be carried out at a given time while the second one has to do with informational content, which must be retrieved, i.e., what we already know. This type of memory relies on other cognitive functions such as working memory, divided attention, executive functions, all of which show age-related deficits. Although prospective memory refers in effect to everyday memory and has a range of consequences if it fails, it remains an area of research that only recently has attracted more scientific interest [89]. So far, only few studies have been conducted and investigated more thoroughly the impact that this type of memory has on the demented patients’ daily living.

It is widely recognized that issues related to prospective memory are prevalent in aging [90], with these challenges being particularly evident in individuals with dementia [91]. Considering that aging represents the primary risk factor for developing dementia [92], there is a substantial need for the development of innovative and effective interventions to aid older adults in remembering their daily activities. These interventions encompass cognitive training techniques, such as intention implementation [93], as well as the utilization of uncomplicated technical devices to facilitate medication reminders [94].

A further distinction of the prospective memory has been made between event and time-based prospective memory [95]. According to this distinction event-based prospective memory involves remembering to perform a certain action when an external cue is given, such as remembering to phone someone when a picture of him/her is provided [55]. Time-based prospective memory involves remembering to perform a certain action at a specific time or after certain time has passed, for example taking medication ten minutes after lunch [55]. Furthermore, in [96], a distinction is made between pulse intentions, which require execution at a specific time, and step intentions, which have a more flexible timeframe for completion (e.g., “I need to call the bank at some point today”). These distinctions hold significance in clinical assessments.

To this end, the studies assessing prospective memory compare performance of older healthy adults to that of AD patients or traumatic brain injury (TBI) patients in a variety of tasks. Nevertheless, there is a scarcity of studies comparing the performance of patients suffering from other forms of dementia to that of healthy subjects, or investigating prospective memory in patients with dementia independently, except for the research presented in [77].

There are a limited number of studies so far that have addressed the issue of whether there is a link between prospective memory and daily living activities and quality of life in older adults, or the way that age related decline of prospective memory can affect the daily function of the elderly. In this line of work, it was found that the application of a computer game (the Virtual Week task) for the assessment of prospective memory, significantly aided performance of healthy older adults on related tasks [97]. Similarly, [98,99] observed a general enhancement in the prospective memory of the participants, indicating positive advantages of this training approach. In a systematic qualitative analysis, coupled with a quantitative meta-analysis on the impact of prospective memory (PM) training in older adults, it was indicated that there was a notable but modest immediate effectiveness of PM training in enhancing PM performance. However, no significant long-term effectiveness was discerned [100]. Similarly, reviews proposed that not only the specific training strategies employed for the assessment of prospective memory need to be further examined, but also certain parameters need to be considered, such as the participants’ digital literacy as well as their motor and sensory restrictions [101,102].

In one of the first studies that compared healthy controls to mildly affected AD patients and patients with dementia in a range of prospective memory tasks [37], it was proposed that on prospective memory tasks the performance of individuals with mild AD was similar to that of patients with dementia. In a later study, event-based and time-based intentions were examined in participants with AD and in healthy controls [38]. The researchers discovered that individuals with Alzheimer’s disease (AD) exhibited poorer performance compared to healthy controls in recalling both time-based and event-based intentions. Consistent findings were reported in another study where patients with dementia demonstrated difficulties in their prospective memory, especially in the context of event-based tasks [39]. In a study involving 14 patients with memory impairments who were assessed in two types of prospective memory tasks (event-based PM and time-based PM), each under errorless learning (EL) and errorful encoding (EF) learning conditions, the results indicate an advantage of EL for the EBPM task but not for the TBPM task [77]. Problems with time-based intentions and event-based intentions are further supported in a more recent study [40].

Finally, it was found that the introduction of a memory encoding strategy could improve prospective memory in healthy older adults and in patients suffering from AD [103].