The main inspiration behind the primary hypothesis of this paper i.e., that Cg25 is centrally involved in repression, was Mayberg's paper on DBS for the treatment of severe depression . The findings of this study have a special significance for Freudian metapsychology. It has been inferred in this paper that the sudden lifting of negative affect upon stimulation of Cg25 is consistent with the idea of a release of libido for object cathexis after it has been pathologically 'dammed up' behind a central repressing force. However, the therapeutic response to stimulation raises some difficult questions for both psychoanalysis and psychiatry. One important question concerns the economy of psychical energy in relation to depression and mania. Freud discussed the issue of mania towards the end of 'Mourning and melancholia':
'The impression which several psycho-analytic investigators have already put into words is that the content of mania is no different from that of melancholia, that both disorders are wrestling with the same "complex", but that probably in melancholia the ego has succumbed to the complex whereas in mania it has mastered it or pushed it aside. Our second pointer is afforded by the observation that all states such as joy, exultation or triumph, which give us the normal model for mania, depend on the same economic conditions. What has happened here is that, as a result of some influence, a large expenditure of psychical energy, long maintained or habitually occurring, has at last become unnecessary, so that it is available for numerous applications and possibilities of discharge' .
Neuroimaging studies of manic patients have shown that in direct contrast to depression, resting state activity is decreased in the OFC [249, 250] and increased in dorsal frontal areas during manic episodes [250, 251]. It is significant that the early responses to Cg25 stimulation do not appear to switch patients from pathological depression to overt mania. According to Freud's model, manic episodes depend on a quantity of dammed-up libido being suddenly made available for object cathexis.
'An important element in the theory of repression is the view that repression is not an event that occurs once but that it requires a permanent expenditure [of energy]. If this expenditure were to cease, the repressed impulse, which is being fed all the time from its sources, would on the next occasion flow along the channels from which it had been forced away, and the repression would either fail in its purpose or would have to be repeated an indefinite number of times. Thus it is because drives are continuous in their nature that the ego has to make its defensive action secure by a permanent expenditure [of energy]' .
In the long term it is feasible that abeyance of repression leads to a therapeutic shift in the energetic equilibrium of the mind; but even if this is true, we still need to consider why upon release from repression, we do not see a pathological release of primitive drive and repressed memory. Are we to assume that electrical stimulation of Cg25 removes both the physiological and psychological causes of depression? Even if depression is primarily an energetic phenomenon and the physiological causes are the psychological causes (and vice versa), wouldn't there still remain memory traces and exogenous stressors facilitating a recall of lost objects, regretted behaviours and eluded ideals?
One possible reason why the effect of Cg25 stimulation appears to have a sustained beneficial effect  rather than an iatrogenic one  may be that inhibiting activity in Cg25 facilitates the disintegration of a wider network. For example, it is possible that activation of Cg25 supports activation of the DMN and deactivation of Cg25 supports deactivation of the DMN and activation of the ON. This model would account for the diminished self focus (ego cathexis) and rejuvenated task focus (object cathexis) seen upon Cg25 stimulation. It may be possible to test this formulation through neuroimaging studies of patients undergoing Cg25 stimulation. If the ego is dependent on repression, we would expect to see decreased activity in the DMN, decreased activity in Cg25 and increased activity in the ON after stimulation. Preliminary evidence lends support to this model . Evidence supporting the interdependency of the ego and repression would of course have important implications for the history of the evolution of human consciousness.
In order to test the validity of the Freudian model, it is important that there be thorough psychophenomenological and neurophysiological analyses of Cg25 and NAc stimulations. Ideally, subjective and objective measures should be taken simultaneously, in real time. If, as this paper predicts, Cg25 is centrally involved in repression, then in addition to dramatic improvements in energy/libido we would also expect to see some adverse responses to stimulation, such as disinhibited behaviour, pathological drive, perseverance, hostility, aggression, sexual promiscuity and a reduced capacity to consider others. Such behaviours are commonly associated with ventromedial prefrontal lesions [255–259]. We would also predict that patients undergoing Cg25 stimulation would be more susceptible to temporal lobe phenomena (such as déjà vu) as a result of diminished inhibitory control over excitatory medial temporal structures. If electrophysiological recordings are carried out, we would hypothesise that electrodes placed within the proximity of septal, supramammillary or hippocampal theta structures would display characteristic bursts of high voltage rhythmic theta during moments of strong emotion (, see  for a review). We would also predict that intracranial EEG recordings in bipolar patients would reveal significant changes in activity paralleling shifts in mood i.e., Cg25 hyperactivity/NAc hypoactivity during depression and Cg25 hypoactivity/NAc hyperactivity during mania.
It is acknowledged that very little in the way of counter evidence has been cited in this paper challenging the validity of the Freudian model. It is likely that several examples could be found in Freud's evolving work of hypotheses that do not correspond well with the findings of modern clinical research. However, it must be emphasised that what we have brought together in this paper are principal concepts of Freudian metapsychology together with principal findings of neuropsychiatry. It is all the more significant therefore that the meeting has been complementary.
In order to develop a discussion of the comparative merits of psychological paradigms, it is worth reminding ourselves of the two main aims of this paper: (1) to propose a series of hypotheses correlating neurophysiological processes with some fundamental processes of psychoanalysis, and (2) to highlight correspondences between Freud's writings in 'Mourning and melancholia' and current findings in depression. How successful these tasks have been will largely depend on two factors: (1) whether evidences from other fields converge with the evidences reviewed here, and (2) whether the psychoanalytic perspective is given credence. There is already ample evidence to support the role of Cg25, the vmPFC and OFC in suppressing primitive affect, but the psychoanalytic significance of this function has yet to be fully appreciated.
It has been said before that it matters little which psychological discipline we choose to derive our operational terms; the approach is secondary to the phenomena:
'Listen my friend, the golden tree of life is green, all theory is grey' .
Psychological models do serve a purpose however, but to provide comprehensive explanations of mental states and behaviours, effective models must evolve naturally from their phenomena. In a recent letter published in a reputable journal and co-signed by a number of leading researchers  a proposal was put-forward as part of a 'decade of the mind' initiative to work towards a transdisciplinary explanation of mental phenomena. The main psychological discipline championed by the authors was cognitive psychology. While the essential idea is a commendable one, we must ask ourselves seriously whether the information processing paradigm is really the best model for carrying out this initiative. The psychological limitations of the behavioural model have been recognised for several decades but the cognitive approach, which views the human mind as an information processor is currently the favoured model of clinicians and researchers. If the computer analogy is an accurate representation of the human psyche, then we can feel comfortable going into the final years of the 'decade of the mind' that real progress will be made. If however, the model is at all incomplete, we may need to consult alternative paradigms to assist our empiricism. The information processing model has traditionally been put to good use guiding and informing empirical research. However, several researchers are now recognising that the computational model has limitations, especially when it is applied to human emotion [62, 68, 262, 263]. What we hope psychoanalysis can bring to the table therefore, is a psychological model that has its roots set firmly in human experience. We hope psychoanalysis can work alongside cognitive psychology to provide a more comprehensive understanding of human experience.
' [T]he mind would often slip through the fingers of psychology, if psychology refused to keep a hold on the mind's unconscious states' .
'Psychoanalysis still represents the most coherent and intellectually satisfying view of the mind that we have' .
The primary requirement for a scientific psychoanalysis is (and always has been) to confirm beyond reasonable doubt that the unconscious mind exists and that it is not only important but essential for an understanding of the human mind and behaviour. If, as this paper maintains, the unconscious does exist, then regardless of the words chosen to define it, the establishment of its phenomenology as subject matter worthy of scientific investigation is important. Deciding how best to test and confirm the hypothesis that the unconscious mind exists will present us simultaneously with a direction towards studying its form and physiology. Due to the rigour of repression, depression is not the easiest phenomenon to gain a perspective on the workings of the unconscious. The psychoses provide a better vantage:
'Things that in the neuroses have to be laboriously fetched up from the depths are found in the psychoses on the surface, visible to every eye' .
' [M]aterial which is ordinarily unconscious can transform itself into preconscious material and then become conscious – a thing that happens to a large extent in psychotic states. From this we infer that the maintenance of certain internal resistances is a sine qua non of normality' .
In depression we only assume the existence of the unconscious through a process of deduction based on ostensibly irrational behaviours (e.g., self-harm, violent self-criticism etc). As Freud made clear, there are much better ways of studying the unconscious and the free-flowing psychical energies that are its signature. Freud first stumbled across a realisation of the unconscious through his work on dissociative states :
' [O]ne received the clearest impression – especially from the behaviour of subjects after hypnosis – of the existence of mental processes that one could only describe as "unconscious". The "unconscious" has it is true, long been under discussion among philosophers as a theoretical concept; but now for the first time, in the phenomena of hypnotism, it became something actual, tangible and subject to experiment' .
'To most people educated in philosophy the idea of anything psychical which is not also conscious is so inconceivable that it seems to them absurd and refutable simply by logic. I believe this is only because they have never studied the relevant phenomena of hypnosis and dreams, which – quite apart from pathological manifestations – necessitate this view. Their psychology of consciousness is incapable of solving the problems of dreams and hypnosis' .
For Freud, dreams were a way of studying the unconscious – unfettered by waking consciousness but the phenomenology of dreaming has largely failed to convince sceptics of the existence of the unconscious. Freud acknowledged that converging lines of enquiry would be required to consolidate the insights gained through the study of dreams:
'Thus, the psychological hypotheses to which we are led by an analysis of the process of dreaming must be left, as it were, in suspense, until they can be related to the findings of other enquiries which seek to approach the kernel of the same problem from another angle' .
Future work may provide the necessary evidence. Alternative means of studying the unconscious – perhaps by way of a pharmacological agent such as a psychedelic drug [193, 266] may open up fresh angles of enquiry. Freud famously described the interpretation of dreams as 'the royal road to a knowledge of the unconscious activities of the mind' . However, dreaming occurs in sleep, making real-time recitation of subjective phenomena impossible. If we could stimulate the primary psychical process in waking we would have a more effective method for studying the unconscious:
'Freud once said of dreams that they were the via regia or royal way to study the unconscious; to an even greater degree this seems to be true for the LSD experience' .
It is anticipated that progress towards a wider appreciation of the psychoanalytic model will first require confirmation of the existence of the unconscious mind. We propose that the most effective way of achieving this is to stimulate the primary psychical process in waking consciousness. There is a wealth of evidence to suggest that this can be reliably achieved through the use of a psychedelic drug such as LSD [193, 266–285]:
'One must...put it simply, it does seem that all LSD does is open the doors to the unconscious' .
Using neuroimaging techniques we would predict that the ego dissolving, primary process releasing properties of a psychedelic compound would correspond with a shift in effective connectivity in the DMN, with the medial temporal regions (as opposed to the vmPFC) exerting principal causality [33, 121, 286, 287]. Testing this hypothesis will be difficult, but such challenging procedures are necessary if the primary psychical process is to be considered a matter worthy of investigation. Once we are better able to study the phenomenology of the unconscious, the application of our new knowledge to the study and treatment of the whole of the mind will follow more easily.